arXiv subjects

John Derek Demaree

Publications and source records attributed to John Derek Demaree.

3 recordsLinked to original sources

arXiv2026

Magnetic Order in Pulsed Laser Deposited (Fe,Ni)5GeTe2 Films

We report the successful growth of highly textured thin films of (Fe,Ni)5GeTe2 two-dimensional ferromagnet on c-plane sapphire using pulsed laser deposition. Structural characterization via X-ray diffraction confirms preferential orientation along the (000l) direction, indicative of a high crystallographic texture. These films of van der Waals (vdW) type interplanar bonding exhibit robust ferromagnetism with a Curie temperature reaching ~ 498 K. Electrical transport measurements reveal a clear anomalous Hall effect, with an anomalous Hall conductivity and Hall angle (%) of ~ 20 Ohm-1cm-1 and ~ 0.90, respectively. Furthermore, the magnetoresistance displays a pronounced dependence on film thickness, highlighting the tunability of spin-dependent transport in these vdW ferromagnetic thin films.

cond-mat.mtrl-sci↗

arXiv2026

Magneto Transport and Spin Reorientation in Pt Co78Ho22 Heterostructures Near the Sublattice Compensation Temperature

Metallic amorphous ferrimagnets of 3d transition metals (TM) and rare earths (RE) with 4f electrons exhibit rich magneto transport behavior due to the interplay between the 3d and 4f magnetic sublattices and their interaction with mobile charges. Tuning the TM and RE concentrations in the alloy can effectively modulate the compensation temperature, where the moments of the two sublattices point in opposite direction leading to a net zero magnetization. Despite extensive magnetotransport studies in Gd and Tb based 3d 4f systems, Ho based alloys remain comparatively underexplored, even though Ho possesses the largest orbital angular momentum (OAM) among the lanthanides. This unquenched OAM can strongly impact magnetic anisotropy and magnetotransport in ferrimagnetic heterostructures. Here, we have investigated the anomalous Hall resistivity , dc magnetization, and spin Hall magnetoresistance (SHMR) of Co78Ho22.Al film and a Pt.Co78Ho22.Al heterostructure deposited using multitarget magnetron sputtering. The Hall resistivity of both systems shows a distinct sign reversal and prominent wing-shaped hysteresis loops in the vicinity of the compensation temperature (Tcomp), which is accompanied by the minimum saturation magnetization near Tcomp. Furthermore, the SHMR in Pt.Co78Ho22.Al film is enhanced due to the Pt layer. These HM interface-induced prominent features of magneto-transport are addressed in the light of the existing theories of spin flop transitions, spin orbit torque, and microscopic phase separation, which may lead to the formation of 3d and 4f magnetic clusters in the film.

cond-mat.mtrl-sci↗

arXiv2026

Selenization of V$_2$O$_5$/WO$_3$ Bilayers for Tuned Optoelectronic Response of WSe$_2$ Films

Scalable and controlled doping of two-dimensional transition metal dichalcogenides is essential for tuning their electronic and optoelectronic properties. In this work, we demonstrate a robust approach for substitution of vanadium in tungsten diselenide (WSe$_2$) via the selenization of pre-deposited V$_2$O$_5$/WO$_3$ thin films. By adjusting the thickness of the vanadium oxide layer, the V concentration in W$_{1-x}$V$_x$Se$_2$ is systematically varied. Electrical measurements on field-effect transistors reveal a substantial enhancement in hole conduction, with drain current increasing by nearly three orders of magnitude compared to undoped WSe$_2$. Temperature-dependent electrical resistivity indicates a clear insulator-to-metal transition with increasing V content, likely due to band structure modifications. Concurrently, the photoconductive gain decreases, suggesting enhanced recombination and charge screening effects. These results establish vanadium doping via selenization of V$_2$O$_5$/WO$_3$ films as a scalable strategy for modulating the transport and photoresponse of WSe$_2$, offering promising implications for wafer-scale optoelectronic device integration.

cond-mat.mes-hall↗