Local electromagnetic properties of magnetic pnictides: A comparative study probed by NMR measurement

TL;DR

This study uses NMR measurements to compare the local electromagnetic properties of magnetic pnictides PrCoAsO and NdCoPO, revealing insights into their magnetic interactions, spin fluctuations, and charge-spin coupling.

Contribution

It provides a comparative analysis of 75As and 31P NMR data in different pnictides, highlighting the role of interlayer separation and 4f moments in their magnetic behavior.

Findings

Antiferromagnetic interaction between 4f moments in PrCoAsO.

Linear variation of quadrupolar coupling with spin susceptibility.

Three-dimensional ferromagnetic spin fluctuations in NdCoPO.

Abstract

75As and 31P NMR studies are performed in PrCoAsO and NdCoPO respectively. The Knight shift data in PrCoAsO indicate the presence of an antiferromagnetic interaction between the 4f moments along the c axis in the ferromagnetic state of Co 3d moments. We propose a possible spin structure in this system. The 75As quadrupolar coupling constant, $\nu_Q$ increases continuously with the decrease of temperature and is found to vary linearly with the intrinsic spin susceptibility, Kiso. This indicates a possibility of the presence of a coupling between charge density and spin density fluctuations. Further, 31P NMR Knight shift and spin lattice relaxation rate (1/T1) in the paramagnetic state of NdCoPO indicate that the differences between LaCoPO and NdCoPO with SmCoPO are due to the decrement of inter layer separation and not due to the moments of 4f electrons. Nuclear spin lattice relaxation time (T1) in NdCoPO shows weak anisotropy at 300 K. Using self consistent renormalization (SCR)theory of itinerant ferromagnet, it is shown that in the ab plane, the spin fluctuations are three dimensional ferromagnetic in nature. From SCR theory the important spin fluctuation parameters ($T_0$, $T_A$, $\bar{F}_1$) are evaluated. The similarities and dissimilarities of the NMR results in As and P based systems, with different rare earths have also been discussed.