Influence of magnetic impurities on the heat capacity of nuclear spins

TL;DR

This paper investigates how magnetic impurities affect nuclear spin heat capacity, revealing a $T^{-1}$ dependence caused by impurity-induced nuclear-spin polarization, controlled by a specific magnetic moment ratio rather than impurity concentration.

Contribution

It introduces a new theoretical understanding that the nuclear heat capacity's behavior is governed by the ratio of electron to nuclear magnetic moments, not impurity concentration.

Findings

Small magnetic impurities induce a $T^{-1}$ heat capacity dependence.

The key controlling parameter is the ratio of magnetic moments, $rac{ ext{electron}}{ ext{nucleus}}$, not impurity concentration.

The effect persists across a wide temperature and magnetic field range.

Abstract

It is found that in a wide range of temperatures and magnetic fields even a small concentration of magnetic impurities in a sample leads to a $T^{-1}$ temperature dependence of the nuclear heat capacity. This effect is related to a nuclear-spin polarization by the magnetic impurities. The parameter that controls the theory turns out not to be the impurity concentration $C_{imp}$ but instead the quantity $c_{imp} \mu_e / \mu_n$, where $\mu_e$ and $\mu_n$ are the magnetic moments of an electron and a nucleus, respectively. The ratio of $\mu_e$ and $\mu_n$ is of order of $10^3$.