Field-induced transition of the magnetic ground state from A-type antiferromagnetic to ferromagnetic order in CsCo2Se2

TL;DR

This study investigates the magnetic phase transition in CsCo2Se2, revealing a switch from A-type antiferromagnetic to ferromagnetic order under an applied magnetic field, highlighting its complex magnetic interactions.

Contribution

It provides the first detailed characterization of the magnetic phase diagram of CsCo2Se2, including field-induced transitions and weak magnetic coupling, linking it to related superconducting materials.

Findings

CsCo2Se2 exhibits A-type antiferromagnetic order below 66 K.

A metamagnetic transition occurs at approximately 0.3 T.

Full ferromagnetic saturation is achieved around 6.4 T.

Abstract

We report on the magnetic properties of CsCo$_2$Se$_2$ with ThCr$_2$Si$_2$ structure, which we have characterized through a series of magnetization and neutron diffraction measurements. We find that CsCo$_2$Se2$_2$ undergoes a phase transition to an antiferromagnetically ordered state with a N\'eel temperature of $T_{\rm N} \approx$ 66 K. The nearest neighbour interactions are ferromagnetic as observed by the positive Curie-Weiss temperature of $\Theta \approx$ 51.0 K. We find that the magnetic structure of CsCo$_2$Se$_2$ consists of ferromagnetic sheets, which are stacked antiferromagnetically along the tetragonal \textit{c}-axis, generally referred to as A-type antiferromagnetic order. The observed magnitude of the ordered magnetic moment at $T$ = 1.5 K is found to be only 0.20(1)$\mu_{\rm Bohr}$/Co. Already in comparably small magnetic fields of $\mu_0 H_{MM}$(5K) $\approx$ 0.3 T, we observe a metamagnetic transition that can be attributed to spin-rearrangements of CsCo$_2$Se$_2$, with the moments fully ferromagnetically saturated in a magnetic field of $\mu_0 H_{\rm FM}$(5K) $\approx$ 6.4 T. We discuss the entire experimentally deduced magnetic phase diagram for CsCo$_2$Se$_2$ with respect to its unconventionally weak magnetic coupling. Our study characterizes CsCo$_2$Se$_2$, which is chemically and electronically posed closely to the $A_xFe_{2-y}Se_2$ superconductors, as a host of versatile magnetic interactions.