arXiv subjects

Rudheer Bapat

Publications and source records attributed to Rudheer Bapat.

4 recordsLinked to original sources

arXiv2025

Four-fold Anisotropic Magnetoresistance in Antiferromagnetic Epitaxial Thin Films of MnPt$_{x}$Pd$_{1-x}$

Antiferromagnets are emerging as promising alternatives to ferromagnets in spintronics applications. A key feature of antiferromagnets is their anisotropic magnetoresistance (AMR), which has the potential to serve as a sensitive marker for the antiferromagnetic order parameter. However, the underlying origins of this behavior remains poorly understood, particularly, in thin film geometries. In this study, we report the observation of AMR in epitaxial thin films of the collinear L1$_{0}$ antiferromagnet MnPt$_{x}$Pd$_{1-x}$. In the thicker films, AMR is dominated by a non-crystalline two-fold component, which emerges from domain reconfiguration and spin canting under applied magnetic field. As the film thickness is reduced, however, a crystalline four-fold component emerges, accompanied by the appearance of uncompensated magnetic moment, which strongly modifies the magnetotransport properties in the thinner films. We demonstrate that interfacial interactions lead to a large density of states (DOS) at the Fermi level. This enhanced DOS, combined with disorder in the thinner films, stabilizes the uncompensated moment and results in a four-fold modulation of the DOS as the Neel vector rotates, explaining the observed AMR behavior.

cond-mat.mtrl-sci↗

arXiv2022

Spin-Polarisation measurement using NbN-Insulator-Ferromagnet Tunnel Junction with oxidized barrier

We report a two-step process for the fabrication of superconductor-insulator-normal metal tunnel junctions using NbN as the superconducting electrode and its surface oxide as the insulating tunnel barrier, and investigate its efficacy in measuring spin-polarisation of ferromagnets using the Meservey-Tedrow technique. We observe that for NbN film thickness below 10 nm, under the application of parallel magnetic field, the superconducting density of states show clear "Zeeman" splitting into spin-up and spin-down sub-bands. Tunnelling measurements on devices where ferromagnetic Co is used as the normal electrode shows that these devices can be used to reliably measure spin polarisation of a ferromagnet at temperatures up to 1.6 K. The simplicity of our fabrication process, and the ability to perform spin-polarisation measurements at 4He temperatures makes NbN a very attractive candidate for spin polarisation measurements.

cond-mat.supr-con↗

arXiv2020

Superconductivity in amorphous RexZr (x ~ 6) thin films

We report the growth, characterization and superconducting properties of a new amorphous superconductor, RexZr ( x ~ 6 ), in thin film form. Films were grown by pulsed laser deposition with the substrate kept at room temperature. Films with thickness larger than 40 nm showed a superconducting transition temperature (Tc) of 5.9 K. Superconducting properties were measured for films with varying thickness from 120 to 3 nm. The normal state resistance scales linearly with inverse of thickness. The transition temperature, critical field, coherence length, penetration depth and superconducting energy gap changes marginally with decreasing film thickness down to 8 nm. Scanning tunneling spectroscopy and penetration depth measurements provide evidence for a single gap strong coupling s-wave superconductor. Magneto-transport properties indicate a rich magnetic field-temperature phase diagram with the possibility of vortex liquid phases existing over a large fraction of the mixed state.

cond-mat.supr-con↗

arXiv2018

Magnetocrystalline anisotropy in the Kondo lattice compound CeAgAs$_2$

We report on the single crystal growth and anisotropic physical properties of CeAgAs$_2$. The compound crystallizes as on ordered variant of the HfCuSi$_2$-type crystal structure and adopts the orthorhombic space group $Pmca$~(\#57) with two symmetry inequivalent cerium atomic positions in the unit cell. The orthorhombic crystal structure of our single crystal was confirmed from the powder x-ray diffraction and from electron diffraction patterns obtained from the transmission electron microscope. The anisotropic physical properties have been investigated on a good quality single crystal by measuring the magnetic susceptibility, isothermal magnetization, electrical transport and heat capacity. The magnetic susceptibility and magnetization measurements revealed that this compound orders antiferromagnetically with two closely spaced magnetic transitions at $T_{\rm N1} = 6$~K and $T_{\rm N2} = 4.9$~K. Magnetization studies have revealed a large magnetocrystalline anisotropy due to the crystalline electric field (CEF) with an easy axis of magnetization along the [010] direction. The magnetic susceptibility measured along the [001] direction exhibited a broad hump in the temperature range 50 to 250~K, while typical Curie-Weiss behaviour was observed along the other two orthogonal directions. The electrical resistivity and the heat capacity measurements revealed that CeAgAs$_2$ is a Kondo lattice system with a magnetic ground state.

cond-mat.str-el↗