Spin valves provide a valuable platform to manipulate spin transport, leading to a change in resistivity by changing the direction of applied magnetic field. Here, we present a combined computational and experimental study of a half-metallic full Heusler alloy (FHA), ${\mathrm{Co}}_2\mathrm{NbAl}$, which exhibits spin valve like magnetoresistance (MR) from low temperatures to room temperature (RT) and beyond. ${\mathrm{Co}}_2\mathrm{NbAl}$ crystallizes in the prototype $L{2}_1$ structure with antisite disorder between Co and Al. Magnetization measurements indicate its ferromagnetic (FM) behavior with a Curie temperature $\left({\mathrm{T}}_{\mathrm{C}}\right)$ above RT, making it attractive for device applications. Longitudinal resistivity data indicate its fully half-metallic ferromagnetic (HMF) nature below 84 K and a reasonably high spin polarization at higher T. Hall measurements confirm intrinsic anomalous contribution to dominate in this system. Ab initio calculations confirm the half-metallic nature of the alloy with a total moment of $2 {\mu }_B/\text{f.u.}$ (larger than measured value of $1.56 {\mu }_B/\text{f.u.}$). Antisite disorder between Co and Al sites explains the discrepancy in the net magnetization obtained between theory and experiment. This also discloses an antiferromagnetic (AFM) correlations mediated by Co atoms distributed in an overall FM matrix. The formation of such AFM-FM interfaces often pins the nearby spins, which is possibly responsible for the spin valve effect.

Close

PrevNext

View figure in article

• Magnetism
• Spintronics
• Disordered alloys
• Half-metals
• Heusler alloy
• Spin valves