Magnetic relaxation phenomena in Cu$_2$OSeO$_3$ and phase diagram

TL;DR

This study maps the magnetic phase diagram of Cu$_2$OSeO$_3$ near its critical temperature, revealing complex relaxation dynamics and non-exponential behavior at phase boundaries across a broad frequency range.

Contribution

It provides detailed insights into the magnetic relaxation phenomena and phase boundaries of Cu$_2$OSeO$_3$ using comprehensive DC and AC susceptibility measurements.

Findings

Relaxation times reach several milliseconds at phase borders

Relaxation behavior is non-exponential near phase transitions

Phase boundary determination depends on measurement criteria and frequency

Abstract

We present an investigation of the magnetic field-temperature phase diagram of Cu$_2$OSeO$_3$ based on DC magnetisation and AC susceptibility measurements covering a broad frequency range of four orders of magnitude, from very low frequencies reaching 0.1 Hz up to 1 kHz. The experiments were performed in the vicinity of $T_C=58.2$ K and around the skyrmion lattice A-phase. At the borders between the different phases the characteristic relaxation times reach several milliseconds and the relaxation is non-exponential. Consequently the borders between the different phases depend on the specific criteria and frequency used and an unambiguous determination is not possible.