Weak ferromagnetic spin and charge stripe order in La[sub 5/3]Sr[sub 1/3]NiO[sub 4]

TL;DR

This study investigates the magnetic and charge order in La5/3Sr1/3NiO4, revealing weak ferromagnetism and the effects of high magnetic fields on stripe ordering temperatures, contributing to understanding complex magnetic phases in nickelates.

Contribution

It provides the first detailed phase diagram of La5/3Sr1/3NiO4 under high magnetic fields, highlighting the field-dependent shift of spin stripe order and evidence of weak ferromagnetism.

Findings

Charge stripe order temperature is unaffected by magnetic fields.

Spin stripe order temperature shifts significantly with magnetic field.

Presence of in-plane weak ferromagnetic moments in the charge stripe phase.

Abstract

We present magnetization and specific heat data of a La5/3Sr1/3NiO4 single crystal in high magnetic fields. From the charge and spin stripe ordering temperatures, as well as a magnetic low temperature transition, we have constructed the electronic phase diagram for fields up to 14 Tesla. While the charge stripe ordering temperature TCO is independent of the magnetic field, there is a significant shift of the spin stripe ordering temperature TSO of about 1.5 K/ Tesla, if the magnetic fields are applied parallel to the NiO2-planes. The specific heat measurements indicate a large anomalous entropy change at TCO. In contrast, no significant entropy change is observed at the spin stripe transition. The high field magnetization experiments reveal the presence of in-plane weak ferromagnetic moments in the charge stripe ordered phase. From a phenomenological analysis, the magnetic correlation length of these moments is determined. We suggest that the weak ferromagnetism is due either to the presence of bond-centered charge stripes or to double exchange interactions across site-centered charge stripes.