Quantum Spin Relaxation with THz Attempt Frequency in the 1/3-Fire, 2/3-Ice Ferrimagnet SmMn$_2$Ge$_2$

TL;DR

This study reveals THz-range single-spin relaxation in the ferrimagnet SmMn$_2$Ge$_2$, characterized by a Debye-like resonance and Orbach relaxation, linked to its unique 1/3-fire, 2/3-ice magnetic state.

Contribution

It demonstrates novel single-spin resonance in SmMn$_2$Ge$_2$ with THz attempt frequencies, connecting magnetic state to relaxation dynamics.

Findings

Single-spin resonance observed in SmMn$_2$Ge$_2$

Relaxation energy barrier approximately 840 $k_B$

Attempt frequencies in the THz range

Abstract

Ferrimagnets in which half the spins are disordered and half ordered, so-called half-fire, half-ice state, have been advanced theoretically as a route towards realizing exotic magnetic ground states. Here we demonstrate novel single-spin resonance in SmMn$_2$Ge$_2$, a 1/3-fire, 2/3-ice material. Using ac-susceptibility in the frequency range 0.1 Hz - 1 kHz we find a Debye-like resonance with Orbach relaxation temperature dependence, yielding an energy barrier $E_B \approx 840$ $k_B$ and attempt frequencies in the THz range. These quantities strongly suggest single-spin relaxation among paramagnetic Sm spins where the flipping field is provided by the FM-ordered Mn spins at domain boundaries, a direct outcome of the 1/3-fire, 2/3-ice state.