Tunable Second-Order Structural Transition in As-Deficient MnAs

We report measurements of magnetization, specific heat, and thermal expansion performed on As-deficient MnAs single crystals (MnAs\(_{0.968}\)). Ferromagnetic order is observed near \(T_C \simeq\) 306 K on warming and \(T_C \simeq\) 302 K on cooling, which is consistent with previously-reported valu...

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Bibliographic Details
Published in:arXiv.org 2024-08
Main Authors: White, B D, Huang, K, Fipps, I L, Hamlin, J J, Jang, S, Smith, G J, Xia, B, Simonson, J W, Nelson, C S, Aronson, M C, Maple, M B
Format: Article
Language:English
Subjects:
Anisotropy
Basal plane
Ferromagnetism
Hexagonal lattice
Lattice parameters
Phase transitions
Single crystals
Stoichiometry
Thermal expansion
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Summary:We report measurements of magnetization, specific heat, and thermal expansion performed on As-deficient MnAs single crystals (MnAs\(_{0.968}\)). Ferromagnetic order is observed near \(T_C \simeq\) 306 K on warming and \(T_C \simeq\) 302 K on cooling, which is consistent with previously-reported values for stoichiometric MnAs samples. In contrast, the second-order structural phase transition is observed at \(T_S \simeq\) 353 K, which is nearly 50 K lower than in the stoichiometric compound. We observe differences in the thermal expansion of our samples when compared to reports of stoichiometric MnAs including: (1) the \(\sim\)1.5% volume decrease at \(T_C\) is smaller than the expected value of 1.9%, (2) the lattice parameters perpendicular to the basal plane exhibit a discontinuous jump of \(\sim\)1.1% at \(T_C\) instead of being continuous across \(T_C\), and (3) thermal expansion perpendicular to the basal plane for \(T_C \le T \le\) 315 K is negative rather than positive. We also observe a correlation between the ratio of hexagonal lattice parameters, \(c/a\), and \(T_S\), strongly suggesting that the degree of structural anisotropy in MnAs could play an important role in tuning \(T_S\).
ISSN:2331-8422