Study of electron spin dynamics in grain aligned LaCoPO: an itinerant ferromagnet

TL;DR

This study investigates the electron spin dynamics in LaCoPO using 139La NMR, revealing 3D spin fluctuations and anisotropic Knight shifts, and compares these findings with LaFePO to understand their magnetic behaviors.

Contribution

It provides new insights into the spin fluctuation dimensionality and anisotropy in LaCoPO, and correlates NMR relaxation data with magnetization using SCR theory.

Findings

LaCoPO exhibits strong temperature-dependent and anisotropic Knight shifts.

Presence of 3D spin fluctuations in LaCoPO confirmed by NMR relaxation.

Spin fluctuation parameters align with the universal Rhodes-Wohlfarth curve.

Abstract

139La NMR study was performed in grain aligned (c|| H0) sample of LaCoPO and polycrystalline LaFePO. Knight shift is isotropic and temperature independent in LaFePO. It is strongly temperature dependent and anisotropic in LaCoPO. The spin-lattice relaxation rate in LaCoPO clearly reveals the existence of 3D spin fluctuations both in the paramagnetic and ferromagnetic state over and above the dominant 2D spin fluctuations in the paramagnetic state, observed earlier from 31P NMR measurements in the same oriented sample. The spin fluctuation parameters in LaCoPO determined from 139La NMR relaxation and magnetization data, using the self consistent renormalization (SCR) theory, are in close agreement and follow the universal Rhodes-Wohlfarth curve.