Singlet state formation and its impact on magnetic structure in tetramer system SeCuO$_3$

TL;DR

This study investigates the magnetic structure of SeCuO$_3$, revealing non-collinear antiferromagnetic order below 8 K, evidence of high-temperature singlet state formation, and significant magnetic moment renormalization on copper sites.

Contribution

It provides the first detailed experimental characterization of the magnetic ordering and singlet state formation in SeCuO$_3$, highlighting the impact of singlet states on magnetic structure.

Findings

Non-collinear antiferromagnetic order established below 8 K

Singlet states form on tetramers at temperatures as high as 200 K

Strong renormalization of magnetic moments on copper sites

Abstract

We present an experimental investigation of the magnetic structure in a tetramer system SeCuO$_3$ using neutron diffraction and nuclear resonance techniques. We establish a non-collinear, commensurate antiferromagnetic ordering with a propagation vector $\textbf{k} = \left(0,0,1 \right)$. The order parameter follows a critical behavior near $T_N = 8$ K, with a critical exponent $\beta = 0.32$ in agreement with a 3D universality class. Evidence is presented that a singlet state starts to form on tetramers at temperatures as high as 200 K, and its signature is preserved within the ordered state through a strong renormalization of the ordered magnetic moment on two non-equivalent copper sites, $m_{Cu1} \approx 0.4 \mu_B$ and $m_{Cu2} \approx 0.7 \mu_B$ at 1.5 K.