The role of magnetoelastic coupling and magnetic anisotropy in MnTiO${}_3$

Abstract

We report the thermodynamic properties studied by thermal expansion, magnetostriction, magnetisation, and specific heat measurements as well as the low-energy magnetic excitations of \mto\ and investigate how magneto-elastic coupling and magnetic anisotropy affect the evolution of long-range order and the magnetic phase diagram. Specifically, we utilise high-resolution capacitance dilatometry and antiferromagnetic resonance (AFMR) studies by means of high-frequency electron spin resonance (HF-ESR) spectroscopy. The role of anisotropy is reflected by spin-reorientation at $B_{\mathrm{SF}}$~$\simeq 6$~T and a corresponding sign change in $\partial T_{\mathrm{N}}/\partial B$. Analysis of the AFMR modes enables us to establish the zero-field excitation gap $\Delta$ as well as its temperature dependence. We derive the effective anisotropy field $B_{\mathrm{A}}=0.16(1)$~T which predominately originates from out-of-plane nearest-neighbour dipole-dipole interactions. Despite the nearly fully quenched orbital moment, our data show pronounced thermal expansion and magnetostriction anomalies at $T_{\mathrm{N}}$ and $B_{\mathrm{SF}}$ , respectively, which allows the experimental determination of sizable uniaxial pressure dependencies, i.e., $\partial B_{\mathrm{SF}}/\partial p_{\mathrm{c}}=-0.20(2)$~T/GPa, $\partial T_{\mathrm{N}}/\partial p_b=0.69(12)$~K/GPa, and $\partial T_{\mathrm{N}}/\partial p_c=-2.0(4)$~K/GPa. Notably, short-range magnetic order appears up to at least 3$T_{\mathrm{N}}$ , as indicated by anisotropic lattice distortion, the violation of a constant Grüneisen behavior, and the presence of local magnetic fields detected by HF-ESR.

References in corpus (5)

• Grüneisen parameter studies on heavy fermion quantum criticality
• High-pressure optical floating-zone growth of Li(Mn,Fe)PO${}_4$ single crystals
• Magnetic anisotropy and the phase diagram of chiral MnSb2O6
• Pressure-induced melting of the orbital polaron lattice in La1-xSrxMnO3
• Magnetoelectric coupling tuned by competing anisotropies in Mn${}_{1-x}$Ni${}_x$TiO${}_3$