arXiv subjects

Y. P. Lee

Publications and source records attributed to Y. P. Lee.

5 recordsLinked to original sources

arXiv2019

Goos-Hanchen shift at the reflection of light from the complex structures composed of superconducting and dielectric layers

The Goos-Hanchen effect of light reflected from sandwich (three-layered) structures composed of a superconducting YBa2Cu3O7 film and two different dielectric films is investigated theoretically. It has been shown that optical anisotropy of YBa2Cu3O7 film, as well as its positions in the three-layer specimen, strongly effects on the lateral shift values. We have shown that, for all positions of the superconducting film in the three-layered structure, variation of temperature makes possible to control the values of the lateral shift of TE-polarized light at the incidence angles close to pseudo-Brewster angles, whereas for TM-polarized light the lateral shift is only significant at grazing incidence.

physics.optics↗

arXiv2019

Influence of misfit strain on the Goos-Hanchen shift upon reflection from a magnetic film on a nonmagnetic substrate

The influence of the misfit strain on the lateral shift (Goos-Hanchen effect) experienced by a near-infrared electromagnetic wave upon reflection from the surface of a bilayer consisting of a magnetic, gyrotropic (i.e., whose permittivity tensor elements depend upon magnetization) yttrium-iron garnet film deposited on a nonmagnetic gadolinium-gallium garnet substrate is investigated theoretically. In the geometry of the transverse magneto-optical Kerr effect, it is shown that the mechanical strain near the geometrical film/substrate interface can induce a significant lateral shift of the beam for incidence angles close to normal incidence, where no shift appears in the absence of strain. Our calculations demonstrate positive as well as negative values of the lateral shift, depending on the incident light polarization and on the film thickness. In contrast to that of the misfit strain, the influence of the magnetization of the gyrotropic film on the lateral shift is more noticeable for a TM- than for a TE-polarized wave.

physics.optics↗

arXiv2016

Reinforced magnetic properties of Ni-doped BiFeO3 ceramic

Multiferroic materials attract considerable interest because of the wide range of potential applications such as spintronic devices, data storage and sensors. As a strong candidate for the applications among the limited list of single-phase multiferroic materials, BiFeO3 (BFO) is a quite attractive material due to its multiferroic properties at room temperature (RT). However, BFO is widely known to have large leakage current and small spontaneous polarization due to the existence of crystalline defects such as oxygen vacancies. Furthermore, the magnetic moment of pure BFO is very weak owing to its antiferromagnetic nature. In this paper, the effects of Ni2+ substitution on the magnetic properties of bulk BFO have been investigated. BFO, and BiFe0.99Ni0.01O3, BiFe0.98Ni0.02O3 and BiFe0.97Ni0.03O3 (BFNO: Ni-doped BFO) ceramics were prepared by solid-state reaction and rapid sintering, and analyzed by structural and magnetic-property measurements. The leakage current density was measured at RT by using a standard ferroelectric tester. All the Ni-doped BFO exhibit the similar rhombohedral perovskite structure (R3c) to that of BFO. The magnetic properties of Ni-doped BFO are much enhanced with respect to BFO prepared at the same conditions, since the enhanced ferromagnetic interaction is caused by the Fe/Ni coupling.

cond-mat.mtrl-sci↗

arXiv2009

Giant diamagnetism in half-metallic Co$_{2}$CrAl Heusler alloy

A giant diamagnetism in the Co$_{2}$CrAl compounds, in both bulk and thin film, below a certain temperature ($T_z$) was observed. Above $T_z$, the compound behaves as an ordinary ferromagnet. The diamagnetic alignment might be initiated by the Landau diamagnetism because of the half-metallic properties and the pinning of the diamagnetism is preserved by the peculiar electronic structures.

cond-mat.str-el↗

arXiv2008

Impact of in-plane currents on magnetoresistance properties of an exchange-biased spin-valve with insulating antiferromagnetic layer

The impact of in-plane alternating currents on the exchange bias, resistance, and magnetoresistance of a CoFe/NiCoO/CoFe/Cu/CoFe spin-valve is studied. With increasing current, the resistance is increased while the maximum magnetoresistance ratio decreases. Noticeably, the reversal of the pinned layer is systematically suppressed in both field sweeping directions. Since the NiCoO oxide is a good insulator, it is expected that the ac current flows only in the CoFe/Cu/CoFe top layers, thus ruling out any presence of spin-transfer torque acting on the spins in the antiferromagnetic layer. Instead, our measurements show clear evidences for the influence of Joule heating caused by the current. Moreover, results from temperature-dependent measurements very much resemble those of the current dependence, indicating that the effect of Joule heating plays a major role in the current-in-plane spin-valve configurations. The results also suggest that spin-transfer torques between ferromagnetic layers might still exist and compete with the exchange bias at sufficiently high currents.

cond-mat.mtrl-sci↗