Two-Dimensional Spin Dynamics in the Itinerant Ferromagnet LaCoPO Revealed by Magnetization and $^{31}$P-NMR Measurements

TL;DR

This study uses magnetization and $^{31}$P-NMR measurements to explore the two-dimensional spin dynamics in the layered itinerant ferromagnet LaCoPO, revealing dominant 2D ferromagnetic fluctuations near the Curie temperature.

Contribution

It provides new insights into the 2D nature of spin fluctuations in LaCoPO, a layered itinerant ferromagnet, through detailed NMR and magnetization analysis.

Findings

P nucleus effectively probes magnetic properties.

Characteristic itinerant ferromagnet behavior observed.

Ferromagnetic fluctuations are predominantly two-dimensional.

Abstract

We have performed magnetization and $^{31}$P-NMR measurements on the itinerant ferromagnet LaCoPO (Curie temperature $T_{\rm Curie}\sim 44$ K) with a layered structure in order to investigate spin dynamics in the paramagnetic state. The linear scaling between the Knight shift $K$ at the P site and the bulk susceptibility $\chi$ above $T_{\rm Curie}$ indicates that the P nucleus is suitable for investigating magnetic properties. The temperature and magnetic field dependences of the nuclear spin-lattice relaxation rate divided by the temperature $1/T_1T$ at the P site show characteristic features of itinerant ferromagnets, such as ZrZn$_2$ and Y(Co$_{1-x}$Al$_x$)$_2$. In addition, the relationship between $1/T_1T$ and $\chi$ above $T_{\rm Curie}$ suggests that ferromagnetic fluctuations possess a two-dimensional (2D) characteristic. The present data show that LaCoPO is a unique ferromagnet, where the 2D fluctuations anticipated from the crystal structure are predominant down to almost $T_{\rm Curie}$.