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arXiv · 2309.16168

Magnetism and magnetocaloric properties of Co$_{1-x}$Mn$_x$Cr$_2$O$_4$

Joya A. Cooley·Gregor Dairaghi·Guy C. Moore·Matthew K. Horton·Emily C. Schueller·Kristin A. Persson·Ram Seshadri
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Abstract

Co$_{1-x}$Mn$_x$Cr$_2$O$_4$ crystallizes as a normal spinel in the cubic $Fd \overline{3}m$ space group, and the end members have been reported to display a region of collinear ferrimagnetism as well as a low-temperature spin-spiral state with variable coherence lengths from 3 nm to 10 nm in polycrystalline samples. Here, we present the synthesis of the entire solid solution, and data showing that the ferrimagnetic ordering temperature as well as the spin-spiral lock-in temperature are tunable with the Co/Mn ratio. The peak magnetocaloric entropy change was determined to be $\Delta S_M$ = -5.63 J kg$^{-1}$ K$^{-1}$ in an applied magnetic field change of $\Delta H$ = 0 T to 5 T for the Mn end-member at the ferrimagnetic ordering temperature. Using density functional theory (DFT), we explore the shortcomings of the magnetic deformation proxy to identify trends in $\Delta S_M$ across composition in this spinel system, and explore future extensions of theory to address these discrepancies.

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Joya A. Cooley, Gregor Dairaghi, Guy C. Moore, Matthew K. Horton, Emily C. Schueller, Kristin A. Persson, Ram Seshadri. 2023-09-28. Magnetism and magnetocaloric properties of Co$_{1-x}$Mn$_x$Cr$_2$O$_4$. https://arxiv.org/abs/2309.16168

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