MIGUEL ANDRES RENGIFO MOROCHO
@inma.unizar-csic.es
Instituto de Nanociencia y Materiales de Aragón
RESEARCH, TEACHING, or OTHER INTERESTS
Physics and Astronomy, Engineering
Scopus Publications
Scopus Publications
L. Imhoff, M.B. Di Marco, S.A. Barolin, M.A. Rengifo, M.H. Aguirre, et al.
Ceramics International, 2024
Lara M. Solis, Alberto Anadón, Miguel Rengifo, José Santiso, Juan Carlos Rojas-Sánchez, et al.
2024 IEEE International Magnetic Conference Short Papers Intermag Short Papers 2024 Proceedings, 2024
In this study, we present a systematic investigation of perpendicular magnetic anisotropy and spin dynamics in bismuth-substituted yttrium iron garnet (Bi:YIG) films grown on SGGG[111] substrates using pulsed laser deposition. The films' thickness ranges from 5 nm to 20 nm. Structural characterization, employing X-Ray Diffraction and High-Resolution Transmission Electron Microscopy, shows that the film growth is epitaxial. All the films exhibit a perpendicular magnetic anisotropy component. Additionally, we analyzed the films by performing thermo-spin measurements in on-chip devices. Considering the device's geometry, we successfully quantified the spin Seebeck coefficient and the generated spin current within a Bi:YIG/Pt bilayer. The obtained value of the spin Seebeck coefficient is comparable to conventional YIG/Pt, affirming the potential of this material for efficient spin current generation as an insulating oxide with perpendicular magnetic anisotropy.
G. A. Ramírez, W. Román Acevedo, M. Rengifo, J. M. Nuñez, M. H. Aguirre, et al.
Applied Physics Letters, 2023
In this work, we have investigated the coexistence of volatile and nonvolatile memristive effects in epitaxial phase-separated La0.5Ca0.5MnO3 thin films. At low temperatures (50 K), we observed volatile resistive changes arising from self-heating effects in the vicinity of a metal-to-insulator transition. At higher temperatures (140 and 200 K), we measured a combination of volatile and nonvolatile effects arising from the synergy between self-heating effects and ferromagnetic-metallic phase growth induced by an external electrical field. The results reported here add phase separated manganites to the list of materials that can electrically mimic, on the same device, the behavior of both neurons and synapses, a feature that might be useful for the development of neuromorphic computing hardware.
Miguel Rengifo, Myriam H. Aguirre, Martín Sirena, Ulrike Lüders, Diego Rubi
Frontiers in Nanotechnology, 2022
Neuromorphic computing requires the development of solid-state units able to electrically mimic the behavior of biological neurons and synapses. This can be achieved by developing memristive systems based on ferroelectric oxides. In this work we fabricate and characterize high quality epitaxial BaTiO3-based memristors integrated with silicon. After proving the ferroelectric character of BaTiO3 we tested the memristive response of LaNiO3/BaTiO3/Pt microstructures and found a complex behavior which includes the co-existence of volatile and non-volatile effects, arising from the modulation of the BaTiO3/Pt Schottky interface by the direction of the polarization coupled to oxygen vacancy electromigration to/from the interface. This produces remanent resistance loops with tunable ON/OFF ratio and asymmetric resistance relaxations. These properties might be harnessed for the development of neuromorphic hardware compatible with existing silicon-based technology.
W. Román Acevedo, M. H. Aguirre, C. Ferreyra, M. J. Sánchez, M. Rengifo, et al.
APL Materials, 2022
Memristive systems emerge as strong candidates for the implementation of resistive random access memories and neuromorphic computing devices, as they can mimic the electrical analog behavior or biological synapses. In addition, complementary functionalities, such as memcapacitance, could significantly improve the performance of bio-inspired devices in key issues, such as energy consumption. However, the physics of mem systems is not fully understood so far, hampering their large-scale implementation in devices. Perovskites that undergo topotactic transitions and redox reactions show improved performance as mem systems, compared to standard perovskites. In this paper, we analyze different strategies to optimize the multi-mem behavior (memristive and memcapacitive) of topotactic redox La1/2Sr1/2Mn1/2Co1/2O3−x (LSMCO) films grown on Nb:SrTiO3. We explored devices with different crystallinities (from amorphous to epitaxial LSMCO), out-of-plane orientation [(001) and (110)], and stimulated either with voltage or current pulses. We found that an optimum memory response is found for epitaxial (110) LSMCO stimulated with current pulses. Under these conditions, the system efficiently exchanges oxygen with the environment minimizing, at the same time, self-heating effects that trigger nanostructural and chemical changes that could affect the device integrity and performance. Our work contributes to pave the way for the integration of multi-mem topotactic redox oxide-based interfaces in multiple device architectures, in order to exploit their memristive and memcapacitive properties for data storage or neuromorphic computation.
C. Ferreyra, M. Rengifo, M.J. Sánchez, A.S. Everhardt, B. Noheda, et al.
Physical Review Applied, 2020
Ferroelectric memristors are intensively studied due to their potential implementation in data storage and processing devices. In this work we show that the memristive behavior of metal/ferroelectric oxide/metal devices relies on the competition of two effects: the modulation of metal/ferroelectric interface barriers by the switchable ferroelectric polarization and the electromigration of oxygen vacancies, with the depolarizing field playing a fundamental role in the latter. We simulate our experimental results with a phenomenological model that includes both effects and we reproduce several non-trivial features of the electrical response, including resistance relaxations observed after external poling. Besides providing insight into the underlying physics of these complex devices, our work suggests that it is possible to combine non-volatile and volatile resistive changes in single ferroelectric memristors, an issue that could be useful for the development of neuromorphic devices.
A. Román, M. Rengifo, L.M. Saleh Medina, M. Reinoso, R.M. Negri, et al.
Thin Solid Films, 2017