In-plane ferromagnetism in charge-ordering $Na_{0.55}CoO_2$

TL;DR

This study reveals in-plane ferromagnetism in Na_{0.55}CoO_2 below 20 K, with significant magnetoresistance indicating strong spin-charge coupling in this charge-ordered triangular lattice system.

Contribution

It provides direct experimental evidence of in-plane ferromagnetism in Na_{0.55}CoO_2 and explores its magnetic and transport properties related to charge ordering.

Findings

In-plane ferromagnetism observed below 20 K

Magnetoresistance of 30% at 6 T at low temperatures

Strong spin-charge coupling in the system

Abstract

The magnetic and transport properties are systematically studied on the single crystal $Na_{0.55}CoO_2$ with charge ordering and divergency in resistivity below 50 K. A long-range ferromagnetic ordering is observed in susceptibility below 20 K with the magnetic field parallel to Co-O plane, while a negligible behavior is observed with the field perpendicular to the Co-O plane. It definitely gives a direct evidence for the existence of in-plane ferromagnetism below 20 K. The observed magnetoresistance (MR) of 30 % at the field of 6 T at low temperatures indicates an unexpectedly strong spin-charge coupling in triangle lattice systems.