@article{lopez_tuning_2024,

title = {Tuning of magnetic properties and giant magnetoimpedance effect in multilayered microwires},

author = {Ricardo López and J. P. Andrés and J. A. González and A. García-Gómez and V. Zhukova and A. Chizhik and M. Salaheldeen and A. Zhukov},

url = {https://www.sciencedirect.com/science/article/pii/S2468217924001527},

doi = {10.1016/j.jsamd.2024.100821},

issn = {2468-2179},

year  = {2024},

date = {2024-12-01},

urldate = {2024-12-13},

journal = {Journal of Science: Advanced Materials and Devices},

volume = {9},

number = {4},

pages = {100821},

abstract = {We studied the magnetic properties and Giant Magnetoimpedance (GMI) effect in amorphous Co-rich microwires with similar chemical compositions and different diameters with magnetic (Co, Permalloy) and non-magnetic (Cu) layers deposited by magnetic sputtering onto glass-coating. Studies of magnetic properties and GMI effect of as-prepared microwires and the same microwires with deposited magnetic and non-magnetic layers reveal substantial impact of such layers on GMI effect and hysteresis loops. Both as-prepared samples present soft magnetic properties and high GMI effect. The contribution of magnetic layers is observed in hysteresis loop at higher magnetic field, with hysteresis loops similar to those observed in microwires with mixed amorphous-crystalline structure. Meanwhile, both magnetic and non-magnetic layers affect low field hysteresis loops of both samples. Additionally, the GMI ratio, ΔZ/Z, and magnetic field dependences of GMI ratio are substantially affected by the presence of magnetic and non-magnetic layers deposited onto glass-coating. We discussed the observed experimental dependences considering both change of the internal stresses originated by the sputtered layer as well as the magnetostatic interaction between the amorphous ferromagnetic nucleus and deposited magnetic layers.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pilati_mn-ferrite_2024,

title = {Mn-ferrite nanoparticles as promising magnetic tags for radiofrequency inductive detection and quantification in lateral flow assays},

author = {Vanessa Pilati and María Salvador and Leyre Bei Fraile and José Luis Marqués-Fernández and Franciscarlos Gomes da Silva and Mona Fadel and Ricardo López and María del Puerto Morales and José Carlos Martinez-García and Montserrat Rivas},

url = {https://pubs.rsc.org/en/content/articlelanding/2024/na/d4na00445k},

doi = {10.1039/D4NA00445K},

issn = {2516-0230},

year  = {2024},

date = {2024-08-01},

urldate = {2024-12-13},

journal = {Nanoscale Advances},

volume = {6},

number = {16},

pages = {4247–4258},

abstract = {Lateral flow assays are low-cost point-of-care devices that are stable, easy to use, and provide quick results. They are mostly used as qualitative screening tests to detect biomarkers for several diseases. Quantification of the biomarkers is sometimes desirable but challenging to achieve. Magnetic nanoparticles can be used as tags, providing both visual and magnetic signals that can be detected and quantified by magnetic sensors. In the present work, we synthesized superparamagnetic MnFe2O4 nanoparticles using the hydrothermal coprecipitation route. MnFe2O4 presents low magnetic anisotropy and high saturation magnetization, resulting in larger initial magnetic susceptibility, which is crucial for optimizing the signal in inductive sensors. We functionalized the coprecipitated nanoparticles with citric acid to achieve colloidal stability in a neutral pH and to provide carboxyl groups to their surface to bioconjugate with biomolecules, such as proteins and antibodies. The nanomaterials were characterized by several techniques, and we correlated their magnetic properties with their sensitivity and resolution for magnetic detection in radiofrequency inductive sensors. We considered the NeutrAvidin/biotin model of biorecognition to explore their potential as magnetic labels in lateral flow assays. Our results show that MnFe2O4 nanoparticles are more sensitive to inductive detection than magnetite nanoparticles, the most used nanotags in magnetic lateral flow assays. These nanoparticles present high potential as magnetic tags for the development of sensitive lateral flow immunoassays for detecting and quantifying biomarkers.},

note = {Publisher: RSC},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{salaheldeen_dependence_2024,

title = {Dependence of Magnetic Properties of As-Prepared Nanocrystalline Ni2MnGa Glass-Coated Microwires on the Geometrical Aspect Ratio},

author = {Mohamed Salaheldeen and Valentina Zhukova and Ricardo López and Arcady Zhukov},

url = {https://www.mdpi.com/1424-8220/24/11/3692},

doi = {10.3390/s24113692},

issn = {1424-8220},

year  = {2024},

date = {2024-01-01},

urldate = {2024-12-13},

journal = {Sensors},

volume = {24},

number = {11},

pages = {3692},

abstract = {We have prepared NiMnGa glass-coated microwires with different geometrical aspect ratios, ρ = dmetal/Dtotal (dmetal—diameter of metallic nucleus, and Dtotal—total diameter). The structure and magnetic properties are investigated in a wide range of temperatures and magnetic fields. The XRD analysis illustrates stable microstructure in the range of ρ from 0.25 to 0.60. The estimations of average grain size and crystalline phase content evidence a remarkable variation as the ρ-ratio sweeps from 0.25 to 0.60. Thus, the microwires with the lowest aspect ratio, i.e., ρ = 0.25, show the smallest average grain size and the highest crystalline phase content. This change in the microstructural properties correlates with dramatic changes in the magnetic properties. Hence, the sample with the lowest ρ-ratio exhibits an extremely high value of the coercivity, Hc, compared to the value for the sample with the largest ρ-ratio (2989 Oe and 10 Oe, respectively, i.e., almost 300 times higher). In addition, a similar trend is observed for the spontaneous exchange bias phenomena, with an exchange bias field, Hex, of 120 Oe for the sample with ρ = 0.25 compared to a Hex = 12.5 Oe for the sample with ρ = 0.60. However, the thermomagnetic curves (field-cooled—FC and field-heating—FH) show similar magnetic behavior for all the samples. Meanwhile, FC and FH curves measured at low magnetic fields show negative values for ρ = 0.25, whereas positive values are found for the other samples. The obtained results illustrate the substantial effect of the internal stresses on microstructure and magnetic properties, which leads to magnetic hardening of samples with low aspect ratio.},

note = {Number: 11 

Publisher: Multidisciplinary Digital Publishing Institute},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{gutierrez-perez_high_2023,

title = {High Curie Temperature in Epitaxial D022–Mn3−xGa Ultrathin Films},

author = {Rocío M. Gutiérrez-Pérez and Ricardo López and José T. Holguín-Momaca and Sion F. Olive-Méndez},

url = {https://www.worldscientific.com/doi/10.1142/S2010324723400076},

doi = {10.1142/S2010324723400076},

issn = {2010-3247},

year  = {2023},

date = {2023-06-01},

urldate = {2024-12-13},

journal = {SPIN},

volume = {13},

number = {02},

pages = {2340007},

abstract = {The D0 

2 

2 

22 

–Mn3Ga ferrimagnet promises potential applications in spintronics due to its low magnetization, strong perpendicular magnetic anisotropy and high Curie temperature. In the form of thin and thick films, these properties are preserved. Here, we report on the structural and magnetic characterization of epitaxial D0 

2 

2 

22 

–Mn 

2 

. 

6 

2.6 

Ga ultrathin films with thicknesses of 2 

nm, 5 

nm and 8 

nm grown on Cr buffer layers by magnetron sputtering. We found that the films are perfect single crystals with flat surfaces and Curie temperatures higher than 300 

K. The 2 

nm-thick ultrathin film has higher magnetization than that of the thicker films, likely due to uncompensated ferrimagnetic planes, along the c-axis, linked to the surface roughness at the atomic scale. These properties highly suit the requirements for the elaboration of spintronic devices such as magnetic tunnel junctions.},

note = {Publisher: World Scientific Publishing Co.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{salaheldeen_manipulation_2023,

title = {Manipulation of magnetic and structure properties of Ni2FeSi glass-coated microwires by annealing},

author = {M. Salaheldeen and A. Garcia-Gomez and P. Corte-Leon and A. Gonzalez and M. Ipatov and V. Zhukova and J. Gonzalez and Ricardo López and A. Zhukov},

url = {https://www.sciencedirect.com/science/article/pii/S0925838823003298},

doi = {10.1016/j.jallcom.2023.169026},

issn = {0925-8388},

year  = {2023},

date = {2023-05-01},

urldate = {2024-12-13},

journal = {Journal of Alloys and Compounds},

volume = {942},

pages = {169026},

abstract = {In the current work, we demonstrate that the magnetic and structural properties of Ni2FeSi glass-coated microwires are strongly dependent on annealing conditions. A noticeable change in the magnetic and structural properties has also been compared to as- prepared samples. Annealing conditions increase the crystalline phase content from 34% to 72% for annealing duration 1 h and 6 h, respectively. While as- prepared samples show square hysteresis loops for a wide range of measuring temperatures, annealed samples show inclined hysteresis loops shape. Additionally, a marked increase in coercive and magnetic anisotropy fields has been observed for annealed samples as compared to as- prepared ones at and below room temperature. Meanwhile, highly reduced magnetic remanence was measured in the as-prepared samples. Temperature dependence of the coercivity shows anomalous behavior for as-prepared and annealed samples as well. An increase in the magnetization of the metallic nuclei of Ni2FeSi glass-coated observed in annealed microwire has been attributed to the internal stresses relaxation caused by annealing. The anomalous magnetic behavior at low temperature is due to the coexistence of ordered and disordered phases induced by annealing conditions. The difference in magnetization behavior, remanence, and coercivity values for Ni2FeSi glass-coated microwires samples indicates the influence of internal stresses created by the presence of the glass coating. These findings reveal the sensitivity of Heusler-based glass-coated microwires to temperature and annealing conditions, which will open the door to the design of spintronic devices and sensing applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {In unison magnetization reversal in a magnetoelastic bilayer structure},

author = {N. Cotón and J. P. Andrés and A. Cabrera and M. Maicas and R. Ranchal},

doi = {10.1063/5.0165537},

issn = {0021-8979},

year  = {2023},

date = {2023-01-01},

journal = {Journal of Applied Physics},

volume = {134},

issue = {10},

publisher = {AIP Publishing},

abstract = {Due to the magnetostriction effect, a magnetic material changes its dimensions when it is magnetized. In this work, we show how in a magnetostrictive bilayer structure comprising two materials with magnetostriction constants of opposite signs, the magnetic switching is affected by magnetoelastic coupling. While the layer with positive magnetostriction tries to elongate in the direction of the applied magnetic field, the layer with negative magnetostriction tries to contract. In the studied bilayers, the mechanical influence of each magnetostrictive layer on the other is of the opposite sign because of their opposite magnetostrictive constants. Since magnetoelasticity is not an interfacial interaction but an intrinsic property of magnetic materials, the mechanical strain promoted by the applied magnetic field affects the layers as a whole. The net effect is a simultaneous reversal of magnetization of the two layers regardless of their thicknesses. This behavior has been studied in bilayers with different thickness ratios comprising Ni90Fe10, negative magnetostriction and Fe70Ga30, positive magnetostriction. These results demonstrate the possibility of using this physical mechanism to beat the critical limit thickness imposed by interfacial interactions in magnetically coupled multilayers in such a way that the magnetization reversal is made in unison regardless of the layer thickness.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{salaheldeen_enhancing_2023,

title = {Enhancing the Squareness and Bi-Phase Magnetic Switching of Co2FeSi Microwires for Sensing Application},

author = {Mohamed Salaheldeen and Asma Wederni and Mihail Ipatov and Valentina Zhukova and Ricardo López and Arcady Zhukov},

url = {https://www.mdpi.com/1424-8220/23/11/5109},

doi = {10.3390/s23115109},

issn = {1424-8220},

year  = {2023},

date = {2023-01-01},

urldate = {2024-12-13},

journal = {Sensors},

volume = {23},

number = {11},

pages = {5109},

abstract = {In the current study we have obtained Co2FeSi glass-coated microwires with different geometrical aspect ratios, ρ = d/Dtot (diameter of metallic nucleus, d and total diameter, Dtot). The structure and magnetic properties are investigated at a wide range of temperatures. XRD analysis illustrates a notable change in the microstructure by increasing the aspect ratio of Co2FeSi-glass-coated microwires. The amorphous structure is detected for the sample with the lowest aspect ratio (ρ = 0.23), whereas a growth of crystalline structure is observed in the other samples (aspect ratio ρ = 0.30 and 0.43). This change in the microstructure properties correlates with dramatic changing in magnetic properties. For the sample with the lowest ρ-ratio, non-perfect square loops are obtained with low normalized remanent magnetization. A notable enhancement in the squareness and coercivity are obtained by increasing ρ-ratio. Changing the internal stresses strongly affects the microstructure, resulting in a complex magnetic reversal process. The thermomagnetic curves show large irreversibility for the Co2FeSi with low ρ-ratio. Meanwhile, if we increase the ρ-ratio, the sample shows perfect ferromagnetic behavior without irreversibility. The current result illustrates the ability to control the microstructure and magnetic properties of Co2FeSi glass-coated microwires by changing only their geometric properties without performing any additional heat treatment. The modification of geometric parameters of Co2FeSi glass-coated microwires allows to obtain microwires that exhibit an unusual magnetization behavior that offers opportunities to understand the phenomena of various types of magnetic domain structures, which is essentially helpful for designing sensing devices based on thermal magnetization switching.},

note = {Number: 11 

Publisher: Multidisciplinary Digital Publishing Institute},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Stripe domains in electrodeposited Ni90Fe10 thin films},

author = {N. Cotón and J. P. Andrés and E. Molina and M. Jaafar and R. Ranchal},

doi = {10.1016/j.jmmm.2022.170246},

issn = {03048853},

year  = {2023},

date = {2023-01-01},

journal = {Journal of Magnetism and Magnetic Materials},

volume = {565},

publisher = {Elsevier B.V.},

abstract = {Here we have investigated the formation of stripe domains in electrodeposited Ni90Fe10 films, a metallic alloy with relevant magnetoelastic properties. The X-ray diffractometry patterns confirm the deposition of NiFe with an experimental lattice parameter close to the theoretical value. We have analyzed the influence of both magnetic stirring and an applied magnetic field perpendicular to the sample plane on the formation of stripe domains in Ni90Fe10 films. It is observed the characteristic fingerprint of stripe domains, i.e. the transcritical shape in the in-plane hysteresis loops when the electrolyte is not magnetically stirred during electrodeposition. The quality factor reveals a moderate perpendicular magnetic anisotropy which is confirmed by the stripe periodicity inferred by Magnetic Force Microscopy. In particular, stripe domains are only visible by this technique when the sample thickness is well above the theoretical critical thickness for the stripe domains to be formed. Finally, in samples released after being grown in outward bent flexible substrates it has been promoted an induced in-plane magnetoelastic magnetic anisotropy that reduces the perpendicular magnetic anisotropy. The high quality of the samples studied in this work from the magnetoelastic point of view is reflected by the magnetostriction constant of −22 ppm that it has been experimentally inferred.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{gutierrez-perez_strong_2022,

title = {Strong perpendicular magnetic anisotropy in epitaxial D022-Mn3+xGa ultrathin films},

author = {Rocío M. Gutiérrez-Pérez and Diego I. Zubiate-Pérez and Ricardo López and Maria E. Fuentes-Montero and José T. Holguín-Momaca and Óscar O. Solís-Canto and Adriana Alvídrez-Lechuga and J. A. González and Sion F. Olive-Méndez},

url = {https://www.sciencedirect.com/science/article/pii/S2468023022006885},

doi = {10.1016/j.surfin.2022.102427},

issn = {2468-0230},

year  = {2022},

date = {2022-12-01},

urldate = {2024-12-13},

journal = {Surfaces and Interfaces},

volume = {35},

pages = {102427},

abstract = {Ferrimagnets are highly sought-after materials thanks to their strong perpendicular magnetic anisotropy (PMA) and low magnetization. For example, they are promising materials for current-induced magnetization switching applications. Ferrimagnetic D022-Mn3Ga integrates these properties with a low damping constant and a high Curie temperature. Here, we report a complete analysis of the magnetization and the effective PMA evolution with the thickness of the epitaxial D022-Mn3+xGa ultrathin films. The crystals were grown by magnetron sputtering following two methods: reactive deposition epitaxy and solid phase epitaxy. We found that the uniaxial PMAs and the thickness of the dead magnetic layers differ strongly upon the employed growth method, while saturation magnetizations remain unchanged. Structural defects at the interface due to lattice mismatch and growth method, explain our results. We expose objective estimations of the thermal stability factor Δ, based on the effective PMA in the ultrathin film context. Taking into account our results, D022-Mn3+xGa, in this form, can be employed as the free layer on magnetic tunnel junctions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{robles-cuenca_miniature_2022,

title = {Miniature Autonomous Robot Based on Legged In-Plane Piezoelectric Resonators with Onboard Power and Control},

author = {David Robles-Cuenca and Mario Rodolfo Ramírez-Palma and Víctor Ruiz-Díez and Jorge Hernando-García and José Luis Sánchez-Rojas},

url = {https://www.mdpi.com/2072-666X/13/11/1815},

doi = {10.3390/mi13111815},

issn = {2072-666X},

year  = {2022},

date = {2022-11-01},

urldate = {2023-05-29},

journal = {Micromachines},

volume = {13},

number = {11},

pages = {1815},

abstract = {This work reports the design, fabrication, and characterization of a centimetre-scale autonomous robot with locomotion based on in-plane piezoelectric resonators and 3D-printed inclined legs. The robot consists of a pair of cooperative piezoelectric motors, an electronic power circuit and a battery-powered microcontroller. The piezoelectric motors feature a lead zirconate titanate (PZT) plate of dimensions 20 mm × 3 mm × 0.2 mm vibrating on its first extensional resonant mode at around 70 kHz. A particular position of 3D-printed inclined legs allowed the conversion of the in-plane movement into an effective forward thrust. To enable arbitrary trajectories of the robot on a surface, two parallel piezoelectric plate motors were arranged in a differential drive scheme. The signals to excite these plates were generated by the microcontroller and adapted by a supplementary electronic circuit to increase the effective voltage supplied by the onboard battery. The fully assembled robot had a size of 27 mm × 15 mm and a weight of 7 g and reached a linear speed of approximately 15 mm/s and a rotational speed of up to 50 deg./s. Finally, the autonomous robot demonstrated the ability to follow pre-programmed paths.},

note = {Number: 11 

Publisher: Multidisciplinary Digital Publishing Institute},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{umoh_influence_2022,

title = {Influence of textitex-situ thermal treatment on the chemical states, microstructure and ferroelectrics properties of polycrystalline BiMnO3-δ thin films},

author = {G. V. Umoh and J. T. Holguín-Momaca and R. P. Talamantes and G. Rojas-George and G. Herrera-Pérez and Ricardo López and Francisco Servando Aguirre-Tostado and O. Auciello and S. F. Olive-Méndez and A. Hurtado-Macias},

url = {https://www.sciencedirect.com/science/article/pii/S0040609022002760},

doi = {10.1016/j.tsf.2022.139362},

issn = {0040-6090},

year  = {2022},

date = {2022-08-01},

urldate = {2024-12-13},

journal = {Thin Solid Films},

volume = {756},

pages = {139362},

abstract = {Nanoelectronic devices based on oxide films require materials that may exhibit combined properties such as ferroelectricity, ferromagnetism, and/or ferroelasticity at the same phase. In this sense, multiferroic perovskite BiMnO3-δ thin films exhibit a relevant combination of ferroelectricity and ferromagnetism suitable for device applications. The purpose of this work is to investigate the growth conditions of BiMnO3 thin films using radio-frequency magnetron sputtering and the role of ex-situ thermal treatments under different conditions, which resulted in a P21/c to C2 phase transformation and BiMnO2.93 composition. The crystal structure of the BiMnO3-δ thin films was investigated using X-ray diffraction, high-resolution transmission electron microscopy, ultraviolet-visible spectrophotometer, X-ray photoelectron spectroscopy, and resistivity measurement, to correlate structural and transport properties. The ex-situ thermal treatment was performed in a bismuth and oxygen atmosphere in order to compensate for Bi and O deficiencies. Thus, the result was not an ideal stoichiometric, BiMnO3-δ proved to enhance the ferroelectric properties and other physical properties. The optimized thin films exhibit ferromagnetism up to 37 K, while ferroelectricity remains up to room temperature.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Salaheldeen2022,

title = {Enhancement of Exchange Bias and Perpendicular Magnetic Anisotropy in CoO/Co Multilayer Thin Films by Tuning the Alumina Template Nanohole Size},

author = {Mohamed Salaheldeen and Ayman Nafady and Ahmed M. Abu-Dief and Rosario Díaz Crespo and María Paz Fernández-García and J. P. Andrés and Ricardo López and Jesús A. Blanco and Pablo Álvarez-Alonso},

doi = {10.3390/nano12152544},

issn = {20794991},

year  = {2022},

date = {2022-01-01},

journal = {Nanomaterials},

volume = {12},

issue = {15},

publisher = {MDPI},

abstract = {The interest in magnetic nanostructures exhibiting perpendicular magnetic anisotropy and exchange bias (EB) effect has increased in recent years owing to their applications in a new generation of spintronic devices that combine several functionalities. We present a nanofabrication process used to induce a significant out-of-plane component of the magnetic easy axis and EB. In this study, 30 nm thick CoO/Co multilayers were deposited on nanostructured alumina templates with a broad range of pore diameters, 34 nm ≤ Dp ≤ 96 nm, maintaining the hexagonal lattice parameter at 107 nm. Increase of the exchange bias field (HEB) and the coercivity (HC) (12 times and 27 times, respectively) was observed in the nanostructured films compared to the non-patterned film. The marked dependence of HEB and HC with antidot hole diameters pinpoints an in-plane to out-of-plane changeover of the magnetic anisotropy at a nanohole diameter of ∼75 nm. Micromagnetic simulation shows the existence of antiferromagnetic layers that generate an exceptional magnetic configuration around the holes, named as antivortex-state. This configuration induces extra high-energy superdomain walls for edge-to-edge distance >27 nm and high-energy stripe magnetic domains below 27 nm, which could play an important role in the change of the magnetic easy axis towards the perpendicular direction.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{deltell_martensitic_2021,

title = {Martensitic transformation, magnetic and magnetocaloric properties of Ni–Mn–Fe–Sn Heusler ribbons},

author = {A. Deltell and Abd El-Moez A. Mohamed and P. Álvarez-Alonso and M. Ipatov and J. P. Andrés and J. A. González and T. Sánchez and A. Zhukov and M. L. Escoda and J. J. Suñol and Ricardo López},

url = {https://www.sciencedirect.com/science/article/pii/S2238785421002763},

doi = {10.1016/j.jmrt.2021.03.049},

issn = {2238-7854},

year  = {2021},

date = {2021-05-01},

urldate = {2024-12-13},

journal = {Journal of Materials Research and Technology},

volume = {12},

pages = {1091–1103},

abstract = {Melt-spun ribbons of nominal composition Ni50Mn36-xFexSn14 (x = 0, 2, and 3) were prepared by melt-spinning. The alloys undergo a martensitic transformation from L21 austenite to an orthorhombic 4O martensite on cooling, as determined by X-ray powder diffraction analysis. Replacement of Mn by Fe linearly reduces the characteristic temperatures of the martensitic transformation (the equilibrium temperature decreases from 328 to 285 K) and reduces the Curie temperature of the austenite phase (from 336 to 300 K), whereas the effect of the applied magnetic field on the martensite transition temperatures is negligible. Magnetic measurements (zero-field cooled, ZFC, and field cooled, FC, curves, AC susceptibility measurements) hint the coexistence of two different ferromagnetic martensitic magnetic phases. Moreover, the AC susceptibility measurements and the irreversibility of the ZFC and FC curves point towards the presence of antiferromagnetic and ferromagnetic interactions in the martensitic phase. All samples exhibit spontaneous exchange bias at 2 K, with double-shifted loops, whereas the evolution of the conventional exchange bias with the temperature agrees quite well with the behavior of ferromagnetic regions surrounded by spin-glass regions or with the coexistence of ferromagnetic–antiferromagnetic interactions. Ni50Mn36-xFexSn14 ribbons present a moderate inverse magnetocaloric effect (with a maximum of the magnetic entropy change of 5.7 Jkg−1K−1 for μ0H = 3 T for x = 3). It is worth to note that these materials feature a significant reservoir (up to 44 Jkg−1K−1 for x = 2) of magnetic entropy change, linked to the proximity of the austenitic ferromagnetic transition to the martensitic transformation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{lopez_magneto-transport_2021,

title = {Magneto-Transport Properties of Co–Cu Thin Films Obtained by Co-Sputtering and Sputter Gas Aggregation},

author = {Ricardo López and J. P. Andrés and Mihail Ipatov and J. A. González and Julián González and Valentina Zhukova and Arcady Zhukov},

url = {https://www.mdpi.com/2079-4991/11/1/134},

doi = {10.3390/nano11010134},

issn = {2079-4991},

year  = {2021},

date = {2021-01-01},

urldate = {2024-12-13},

journal = {Nanomaterials},

volume = {11},

number = {1},

pages = {134},

abstract = {Cu100−xCox thin films have been obtained by sputtering (x = 3, 9) and sputter gas aggregation (x = 2.5, 7.5) and subsequent annealing at 400 °C for 1 h. We have studied their structural, magnetic, and magnetotransport properties, both for the as-deposited and annealed samples, confirming the important role of the fabrication method in the properties. The magnetic measurements and the fitting of the hysteresis loops evidence that as-deposited samples consist of superparamagnetic (SPM) and/or ferromagnetic clusters, but in the samples obtained by gas aggregation the clusters are greater (with ferromagnetic behavior at room temperature) whereas in the samples obtained by sputtering, the clusters are smaller and there are also diluted Co atoms in the Cu matrix. The annealing affects negligibly the samples obtained by gas aggregation, but the ones obtained by sputtering are more affected, appearing greater clusters. This behavior is also reflected in the magnetoresistance (MR) measurements of the samples, with different shapes of the MR curves depending on the preparation method: more lineal in the whole range for sputtering, saturation at low fields (about 10 kOe) for gas aggregation. Finally, a Kondo-like minimum in the resistance versus temperature is found in the samples obtained by sputtering, affected by the magnetic field and the annealing. The observed Kondo-like behavior and the influence of annealing on a Kondo-like minimum in sputtered thin films have been attributed to the presence of diluted Co atoms in the Cu matrix and the Co precipitations from the Co–Cu solid solution upon annealing respectively.},

note = {Number: 1 

Publisher: Multidisciplinary Digital Publishing Institute},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hontecillas2021,

title = {Interfacial coupling effect of Cr2O3 on the magnetic properties of Fe72Ga28 thin films},

author = {I. Hontecillas and M. Maicas and J. P. Andrés and R. Ranchal},

doi = {10.1038/s41598-021-92640-y},

issn = {20452322},

year  = {2021},

date = {2021-01-01},

journal = {Scientific Reports},

volume = {11},

issue = {1},

publisher = {Nature Research},

abstract = {Here it is investigated the effect of the antiferromagnet Cr2O3 on the magnetic properties of ferromagnetic Fe72Ga28 thin films. Sputtered Fe72Ga28 layers have their magnetization in the sample plane with a magnetic fluctuation that gives rise to magnetic ripple. In order to turn its magnetization into the out of plane (OOP) direction, it has been magnetically coupled with Cr2O3 that has magnetic moments along the c-axis, that is the perpendicular direction when properly aligned. Cr2O3 has been obtained from Cr oxidation, whereas Fe72Ga28 has been deposited on top of it by sputtering in the ballistic regime. Although a uniaxial in-plane magnetic anisotropy is expected for Fe72Ga28 thickness above 100 nm, the interfacial coupling with Cr2O3 prevents this anisotropy. The formation of stripe domains in Fe72Ga28 above a critical thickness reveals the enhancement of the out of plane component of the Fe72Ga28 magnetization with respect to uncoupled layers. Due to the interface coupling, the Fe72Ga28 magnetization turns into the out-of-plane direction as its thickness is gradually reduced, and a perpendicular magnetic anisotropy of 3·106 erg·cm−3 is inferred from experimental results. Eventually, the coupling between Cr2O3 and Fe72Ga28 promotes an exchange-bias effect that has been well fitted by means of the random field model.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sanchez-Perez2021,

title = {Substrate-Induced Strain Effect on Structural and Magnetic properties of La0.5Sr0.5Co3 films},

author = {Miriam Sánchez-Pérez and J. A. González and Ricardo López and Marco Antonio López de la Torre and Oscar Juan Durá},

year  = {2021},

date = {2021-01-01},

journal = {Nanomaterials},

volume = {11},

pages = {781},

abstract = {We present a detailed study about the substrate-induced strain and thickness effects on the structure and magnetic properties of La0.5Sr0.5CoO3 films. The in-plane tensile or compressive strain imposed by four different substrates configures an in-plane or out-of-plane easy axis, respectively. The presence of a soft magnetic phase at the interface is also conditioned by the type of strain. The obtained results are discussed in terms of the different anisotropies that participate and control the final magnetic behavior. The relevance of these results lies in the feasibility of La0.5Sr0.5CoO3 in memory applications and spintronic devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Strong magnetization and anisotropy of Mn5Ge3thin films on Ge(001)},

author = {Adriana Alvídrez-Lechuga and Ricardo López and Rocío M. Gutiérrez-Pérez and Maria E. Fuentes-Montero and Francisco Espinosa-Magaña and José T. Holguín-Momaca and J. P. Andrés and Sion F. Olive-Méndez},

doi = {10.1088/1361-648X/abe81a},

issn = {1361648X},

year  = {2021},

date = {2021-01-01},

journal = {Journal of Physics Condensed Matter},

volume = {33},

issue = {22},

publisher = {IOP Publishing Ltd},

abstract = {We report on the growth of Mn5Ge3 thin films on Ge(001) substrates following two methods: solid phase epitaxy (SPE) and reactive deposition epitaxy (RDE). We have varied the thickness of the films, in order to study the magnetization and anisotropy evolution. A strongly enhanced magnetization of 1580 kA m-1, compared to 1200 ± 150 kA m-1 for films grown on Ge(111), has been measured on ultrathin films of 5 nm grown by RDE. Thicker films exhibited magnetizations <750 kA m-1. The films grown by SPE also exhibit strong magnetization of 1490 kA m-1 and a drop of magnetization by increasing the film thickness. The effective magnetic anisotropy exhibits a more complex behavior: increases on the SPE films and decreases on the RDE films while increasing the thickness of the films. Magnetostatic and interfacial anisotropies were considered and calculated. The results are discussed in terms of the growth methods and microstructure of the films.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gonzalez2021,

title = {Applied trends in magnetic rare earth/transition metal alloys and multilayers},

author = {J. A. González and J. P. Andrés and Ricardo López},

doi = {10.3390/s21165615},

issn = {14248220},

year  = {2021},

date = {2021-01-01},

journal = {Sensors},

volume = {21},

number = {16},

pages = {1–20},

abstract = {Ferrimagnetic thin films formerly played a very important role in the development of information storage technology. Now they are again at the forefront of the rising field of spintronics. From new, more efficient magnetic recording media and sensors based on spin valves to the promising technologies envisaged by all-optical switching, ferrimagnets offer singular properties that deserve to be studies both from the point of view of fundamental physics and for applications. In this review, we will focus on ferrimagnetic thin films based on the combination of rare earths (RE) and transition metals (TM).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{gutierrez-perez_epitaxial_2020,

title = {Epitaxial growth of the cubic L21-Mn2.6Ga Heusler alloy on MgO(001)},

author = {Rocío M. Gutiérrez-Pérez and José T. Holguín-Momaca and Guo Tian and Shuchi Sunil Ojha and Ricardo López and Caroline A. Ross and Sion F. Olive-Méndez},

url = {https://doi.org/10.1063/5.0001349},

doi = {10.1063/5.0001349},

issn = {0003-6951},

year  = {2020},

date = {2020-04-01},

urldate = {2024-12-13},

journal = {Applied Physics Letters},

volume = {116},

number = {13},

pages = {132407},

abstract = {The Mn3Ga Heusler alloy possesses different crystalline structures representing a range of properties of interest for spintronic applications. We report on the structural and magnetic characterization of the disordered cubic-fcc L21-Mn2.6Ga thin films grown on MgO(001) substrates. The first two nanometers of thickness of the Mn2.6Ga thin films are highly strained to the substrate with a lattice mismatch of 9.54%, playing the role of a template layer for the subsequent growth of relaxed L21-Mn2.6Ga. Once the films reach a critical thickness of 15 nm, the cubic phase reorients its epitaxial relationship from a (001) to a (111) in-plane orientation. Magnetic measurements show that the samples exhibit perpendicular magnetic anisotropy and also that the usually antiferromagnetic L21-Mn3Ga films are ferromagnetic with a Curie temperature >400 K due to partially compensated Mn moments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}