Magnetic properties in layered (K, Rb and Cs)Co2Se2 with ThCr2Si2_type structure

TL;DR

This study investigates the magnetic properties of layered ACo_2Se_2 (A=K, Rb, Cs) single crystals, revealing ferromagnetic transitions around 62-76 K, magnetic moments, and spin fluctuation behaviors within theoretical frameworks.

Contribution

It provides detailed magnetic characterization of ACo_2Se_2 compounds with ThCr_2Si_2 structure, including transition temperatures, magnetic moments, and fluctuation analysis, which were not previously reported.

Findings

Ferromagnetic transition temperatures around 62-76 K.

Effective magnetic moments of Co are approximately 2.0-2.2 μ_B.

Metamagnetism-like behavior observed in CsCo_2Se_2 at 3.5 T.

Abstract

The magnetic properties of ThCr_2Si_2-type single crystals ACo_2Se_2 (A = K, Rb and Cs) have been investigated by magnetic susceptibility and isothermal magnetization measurements at various temperatures. The ferromagnetic phase transition temperatures are estimated as $\approx$ 74 K and 76 K and 62 K for A = K, Rb and Cs (in case of high magnetic field), respectively. The susceptibility data in the paramagnetic state obey the modified Curie-Weiss law quite well and the derived effective magnetic moments of the Co atom are about 2.21, 2.04 and 2.04 \mu_B/Co and the corresponding spontaneous moments derived at the ground state are 0.72, 0.59 and 0.52 \mu_B/Co as well as the generalized Rhodes-Wohlfarth ratios as 3.07, 3.42 and 3.96 for A= K, Rb and Cs, respectively. The magnetic moment aligns within ab-plane and a metamagnetism-like behavior occurs at a field of 3.5 T in CsCo_2Se_2 with H//ab-plane. The magnetic properties in this system were discussed within the frameworks of the self-consistent renormalization (SCR) and Takahashi's theory of spin fluctuations.