Magnetic anisotropy and the phase diagram of chiral MnSb2O6

TL;DR

This study investigates the magnetic phase diagram and low-energy magnon excitations of chiral MnSb2O6, revealing the role of small anisotropy and magnetic fields in determining its complex magnetic phases and spin structures.

Contribution

It provides the first detailed analysis of the magnetic anisotropy, phase transitions, and spin reorientation phenomena in MnSb2O6 using various spectroscopic and thermodynamic measurements.

Findings

Identification of antiferromagnetic resonance modes below 11.5 K.

Determination of small planar anisotropy with zero-field splitting of 20 GHz.

Observation of competing magnetic phases at low temperatures and small magnetic fields.

Abstract

The magnetic phase diagram and low-energy magnon excitations of structurally and magnetically chiral MnSb2O6 are reported. The specific heat and the static magnetization are investigated in magnetic fields up to 9 and 30 T, respectively, while the dynamicmagnetic properties are probed by X-band as well as tunable high-frequency electron spin-resonance spectroscopy. Below TN = 11.5 K, we observe antiferromagnetic resonance modes which imply small but finite planar anisotropy showing up in a zero-field splitting of 20 GHz. The data are well described by means of an easy-plane two-sublattice model with the anisotropy field BA = 0.02 T. The exchange field BE = 13 T is obtained from the saturation field derived from the pulsed-field magnetization. A crucial role of the small anisotropy for the spin structure is reflected by competing antiferromagnetic phases appearing, at T = 2 K, in small magnetic fields at BC1 $\approx$ 0.5 T and BC2 = 0.9 T. We discuss the results in terms of spin reorientation and of small magnetic fields favoring helical spin structure over the cycloidal ground state which, at B = 0, is stabilized by the planar anisotropy. Above TN, short-range magnetic correlations up to >=60 K and magnetic entropy changes well above TN reflect the frustrated triangular arrangement of Mn2+ ions in MnSb2O6.