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José Holanda

Publications and source records attributed to José Holanda.

18 recordsLinked to original sources

Unifying Magnetic, Electrical, and Thermoelectric Responses in a Non-Collinear Antiferromagnet

Non-collinear antiferromagnets offer unconventional routes for controlling magnetic, electrical, and thermoelectric responses through their complex spin configurations and interfacial symmetry. Here, we detect exceptional interfacial properties arising from a non-collinear antiferromagnet by demonstrating a robust and quantitatively consistent exchange-bias response in an IrMn$_3$/Py heterostructure. The system consists of a 10 nm IrMn$_3$ layer coupled to a 5 nm permalloy (Py) film. Longitudinal magneto-optical Kerr effect (MOKE), anisotropic magnetoresistance (AMR), and anomalous Nernst effect (ANE) measurements independently reveal the same unidirectional field shift of approximately 50 Oe, together with a consistent cosine angular dependence. The simultaneous observation of these signatures establishes a direct correspondence between the interfacial magnetic symmetry imposed by the non-collinear antiferromagnet and the responses of the adjacent ferromagnet. This symmetry is manifested consistently in magnetization reversal, charge transport, and thermally driven voltage generation, demonstrating that the exchange-bias imprint is not restricted to a single experimental observable. Our results reveal a coherent multifunctional response of IrMn$_3$/Py and extend the conventional understanding of exchange bias beyond collinear antiferromagnetic systems. More broadly, they demonstrate the potential of non-collinear antiferromagnets as platforms for coupling magnetic, electrical, and thermoelectric functionalities in spintronic and spin-caloritronic devices.

cond-mat.mtrl-sci↗

Resonantly Enhanced Phonon Transport by Magnon Pumping in a Ferromagnetic/Piezoelectric Bilayer

We report the first experimental observation of resonantly enhanced propagating phonon transport induced by magnon pumping in a ferromagnetic/piezoelectric bilayer. Surface acoustic waves (SAWs) generated in a 128$^{\circ}$ Y-cut LiNbO$_3$ delay-line device resonantly excite magnetization dynamics in an adjacent Co film through magnetoelastic coupling. The enhancement of the transmitted acoustic signal occurs exclusively when the SAW frequency satisfies the ferromagnetic resonance condition predicted by the Kittel dispersion, providing a direct experimental fingerprint of resonant magnon-phonon coupling. A systematic comparison between the Co/LiNbO$_3$ bilayer and the bare LiNbO$_3$ substrate demonstrates that the observed transmission enhancement originates solely from the dynamic interaction between propagating phonons and coherent magnetization precession. Furthermore, measurements performed at different SAW harmonics reveal that only the harmonic satisfying the FMR condition produces a measurable enhancement, confirming the frequency-selective nature of the phenomenon. These findings establish an efficient mechanism for transferring energy from magnons to propagating phonons and provide a new strategy for actively controlling coherent acoustic transport in hybrid spintronic, straintronic, and quantum phononic platforms.

cond-mat.mes-hall↗

Detecting a large magneto-optical shift in Py/NiO bilayers

Here, magneto-optical magnetometry measurements on Py/NiO bilayers reveal a pronounced magnetic-field-induced wavelength shift, demonstrating strong magneto-optical coupling in this antiferromagnetic system. A systematic and monotonic spectral shift of up to ~ 400 nm is observed as the applied magnetic field increases, saturating at higher fields. Quantitative analysis shows that the associated magneto-optical energy variation is on the order of 107 eV, comparable to the magnon energy scale in NiO. Owing to the large NiO thickness, the observed effect originates from magnons intrinsic to the antiferromagnetic NiO layer rather than from spin currents injected by the Py underlayer. These results provide direct experimental evidence for magnetic-field control of antiferromagnetic magnon energies via magneto-optical interactions, establishing Py/NiO bilayers as a promising platform for optically probing and manipulating antiferromagnetic spin dynamics.

cond-mat.mes-hall↗

Controlling magnetic damping with spintronic thermal effects in Py/Fe3O4-PANI bilayers

We report experiments that control magnetic damping in Py/Fe3O4-PANI via two spintronic thermal effects: spin Seebeck and anomalous Nernst. Magnetic damping is measured using ferromagnetic resonance (FMR) techniques, where the sample is excited by microwave radiation and the resulting DC voltage is detected in the Fe3O4-PANI film. When a temperature gradient is applied in the longitudinal configuration, the DC voltage linewidth increases or decreases depending on the direction of the thermal gradient. This finding demonstrates that magnetic damping in Py/Fe3O4-PANI can be controlled by currents induced by thermal effects. Remarkably, the absolute linewidth changes observed in Py/Fe3O4-PANI exceed those seen in bilayers of ferrimagnetic insulator yttrium iron garnet and heavy metal by more than an order of magnitude. We interpret the significant change in magnetic damping as a result of intrinsic phenomena occurring in bilayers.

cond-mat.mtrl-sci↗

New method of image processing via statistical analysis for application in intelligent systems

Image processing has always been a topic of significant importance to society. Recently, this field has gained considerable prominence due to the development of intelligent systems. In this work, we present a new method of image processing that utilizes statistical analysis, specifically designed for applications in intelligent systems. We tested our method on a large collection of images to assess its effectiveness.

physics.data-an↗

Enhancement of magnetic spin Hall angle by extrinsic surface roughness

The magnetic spin Hall effect arises from a reactive counterpart of the dissipative spin response that is responsible for the ordinary spin Hall effect. This interpretation is supported by the dependence of spin Hall effect signals on the reversal of magnetic order parameters and can be explained in terms of the symmetries of well-defined linear response functions. This proposal has enabled the generation and manipulation of spin currents electrically. In terms of conversion efficiency, the spin Hall angle is a key parameter used to characterize a material's ability to convert spin currents to charge currents and vice versa. Consequently, there is an ongoing effort to identify mechanisms that can increase the spin Hall angle. In theis work, it is proposed a mechanism based on extrinsic surface roughness, which enhances the magnetic spin Hall angle when the ratio of roughness to thickness is high. This mechanism represents an important discovery that will advance the development of charge-to-spin devices.

cond-mat.mes-hall↗

Observing a quantum magnetic effect in CaYAl3O7-X particles (X=Ni, Fe, Co)

Yttrium calcium aluminate, with the formula CaYAl3O7, has been extensively researched due to its remarkable luminescent properties when doped or co-doped. Additionally, it exhibits exceptional piezoelectric properties at high temperatures. However, the potential magnetic properties this material can acquire through doping or co-doping have largely gone unexplored until now. In this innovative study, we investigate the quantum magnetic characteristics of yttrium calcium aluminate particles doped with transition metals such as cobalt, iron, and nickel. Our magnetic measurements of hysteresis curves in the macroscopic regime reveal intriguing magnetic characteristics that have not been documented in the literature. Given the high applicability of this material in biological microelectromechanical systems, we conducted a detailed study to demonstrate these findings.

cond-mat.mtrl-sci↗

Oscillating Magnetic Effect in BiFeO$_3$

The development of electric vehicles has led to a growing need for more efficient and environmentally friendly batteries. As a result, there is significant interest in researching new materials and techniques to enhance battery efficiency. One such material being explored is bismuth ferrite (BiFeO$_3$ or BFO), a perovskite with versatile properties. Researchers are particularly intrigued by the potential to control its antiferromagnetic magnetization using magnetic or electric fields. Here, a comprehensive analysis of BFO was conducted, with a focus on its behavior when subjected to oscillating magnetic fields. The research revealed that BFO is sensitive to the frequency and shape of these magnetic fields, leading to the discovery of a new effect related to the transmission of electromagnetic signals on its surface. This effect resulted in a significant increase in the power of the electromagnetic signal, representing a major technological breakthrough. According to the findings, this gain in power has not been observed in any system of this kind before. The study also demonstrated that BFO has the ability to detect magnetic fields through electrical output signals and vice versa, which is crucial for assessing the state and efficiency of batteries, thus contributing to significant advancements in energy storage technology.

cond-mat.mtrl-sci↗

Exploring the effects of ultraviolet radiation on the properties of Fe3O4/PANI nanostructures

The properties of any material are the basis for the most diverse applications of science, which allows for the dazzling development of new technologies. In this work, we studied the main properties of nanostructures synthesized under ultraviolet radiation. We show that the nanostructures produced are of excellent quality, which is evidenced by the high stability and quality of the magnetic properties.

cond-mat.mtrl-sci↗

Detecting magneto-optical interactions in nanostructures

Effects due to magneto-optical interactions are responsible for most of the phenomena discovered in optoelectronics and spintronics. Magneto-optical interactions can generate elementary excitations of the order of light-magnetic matter, which can flow under certain conditions. Here, we observe the intensities of magneto-optical interactions in hexagonal arrays of magnetic nanowires using experimental measurements and simulations. Nanowires of three materials (cobalt-Co, iron-Fe, and nickel-Ni) were electrodeposited on alumina membranes by the AC electrodeposition method. Our results reveal that the magneto-optical behavior can produce, under certain conditions, a kind of avalanche of magneto-optical interactions, which is dynamic. Such an observation shows the possibility of generating a magneto-optical current (spin-opto current).

cond-mat.mes-hall↗

Unraveling oscillations at ferro(para)magnetic and non-collinear antiferromagnetic interfaces

Here, we show that the ferro(para)magnetic and non-collinear antiferromagnetic interfaces contribute to oscillating signals observed in the magnetoresistance. We associate the effect with the fact that the spins on the surface of IrMn3 produce instability in the surface magnetoresistance of the material, which is sensitive to the magnetic field. We carried out experiments using bilayers of IrMn3 under permalloy (Py) and IrMn3 under platinum (Pt). The oscillations were intensely evident at the Py/IrMn3 interface and less explicit at the Pt/IrMn3 interface. We carried out the experiments using pulsed current, with a square pulse width of 1μs and amplitudes of 20 μA to 20 mA. The oscillating signals are proportional to the crystallographic direction of the material, the ferromagnetism of the material adjacent to IrMn3, and sensitive to the amplitude of the pulsed current. We believe that observation is a way of transmitting encoded information through magnetoresistance.

physics.app-ph↗

Observation of Damped Oscillations in Chemical-Quantum-Magnetic Interactions

Fundamental interactions are the basis of the most diverse phenomena in science that allow the dazzling of possible applications. In this work, we report a new interaction, which we call chemical-quantum-magnetic interaction. This interaction arises due to the difference in valence that the Fe3O4/PANI nanostructure acquires under certain conditions. In this study, PANI activates the chemical part of the oscillations, leaving the quantum and magnetic part for the double valence effect and consequently for changing the number of spins of the nanostructure sites. We also observed using interaction measurements that chemical-quantum-magnetic interactions oscillate in a subcritical regime satisfying the behavior of a damped harmonic oscillator.

cond-mat.mes-hall↗

Experimental Observation of a Magnetic Interfacial Effect

We observed a magnetic interfacial effect due to the coupling between two interfaces of different materials. The interface is compoust of an antiferromagnetic and other quasi-ferromagnetic material. This effect we measured through the ferromagnetic resonance technique without and with electric current.

cond-mat.mtrl-sci↗

Observation of Spin Current Hermiticity

The spin Hall effect is one of the most relevant effects in spintronics and the key to conversion from charge current into spin current. We report here a phenomenon, which appears in response to the spin Hall effect and represents the anti-polarization of the spin current due to the coupling between interfacial magnetic anisotropies. Such an effect produces a Hermitian spin current. We realized experiments on permalloy (Py) and Cobalt (Co) bilayers to discuss this phenomenon.

physics.app-ph↗

Analyzing the magnetic influence on magneto-optical interactions

Here, we study the magneto-optical interactions in magnetic structures considering the dependence of the interactions with the magnetic field. We perform numerical simulations in a structure of magnetic nanowires, considering them as one chain of strongly interacting single-domain particles. Robustly, we obtain a quantitative value for the interactions, which allows us to classify them into two magnetic states: demagnetized and magnetized.

physics.optics↗

An experimental analysis from the magnetic interactions in nanowire arrays

We study the magnetic interactions experimentally in nanostructures of nanowire arrays. The intensity value obtained from the interactions provides information about its magnetic behavior. We observed two types of experimental magnetic behavior, i. e., demagnetized and magnetized. Our approach represents the first experimental way to analyze the magnetic behavior of a nanostructure considering its magnetic dependence, which is very important for applications in sensors, for example.

cond-mat.mes-hall↗

One Analytical Approach of Rashba-Edelstein Magnetoresistance in 2D Materials

We study analytically the Rashba-Edelstein magnetoresistance (REMR) in a structure made from an insulator ferromagnet, such as yttrium iron garnet (YIG), and a 2D material (2DM) with direct and inverse Rashba-Edelstein effects, such as SLG and MoS$_2$. Our results represent an efficient way of analyzing the Rashba-Edelstein effects.

cond-mat.mtrl-sci↗

Controlled interconversion of quantized spin wave modes via local magnetic fields

In the emerging field of magnonics, spin waves are considered for information processing and transmission at high frequencies. Towards this end, the manipulation of propagating spin waves in nanostructured waveguides for novel functionality has recently been attracting increasing focus of research. Excitations with uniform magnetic fields in such waveguides favors symmetric spin wave modes with odd quantization numbers. Interference between multiple odd spin wave modes leads to a periodic self-focusing effect of the propagating spin waves. Here we demonstrate, how antisymmetric spin wave modes with even quantization numbers can be induced by local magnetic fields in a well-controlled fashion. The resulting interference patterns are discussed within an analytical model and experimentally demonstrated using microfocused Brillouin light scattering (μ-BLS).

cond-mat.mes-hall↗