Effect of static and dynamic disorder on electronic transport of $RCo_2$ compounds: a study of $Ho(Al_xCo_{1-x})_2$ alloys

TL;DR

This study investigates how static and dynamic disorder affect electronic transport and magnetic properties in Ho(Al_xCo_{1-x})_2 alloys, revealing complex resistivity and thermopower behaviors linked to electronic density of states and magnetic fluctuations.

Contribution

It provides new experimental insights into the effects of alloying and temperature on magnetic states and electronic transport in RCo_2-based alloys with itinerant metamagnetic instability.

Findings

Residual resistivity increases with alloying-induced static disorder.

Thermopower shows complex temperature dependence related to electronic density of states.

Resistivity jump at Curie temperature is non-monotonic due to spin fluctuation saturation.

Abstract

We present experimental results on thermoelectric power ({\em S}) and electrical resistivity ($\rho $) of pseudobinary alloys Ho(Al$_x$Co$_{1-x}$)$_2$ ($0 \leq x \leq 0.1 $), in the temperature range 4.2 K to 300 K. The work focuses on the effects of static (induced by alloying) and dynamic (induced by temperature) disorder on the magnetic state and electronic transport in a metallic system with itinerant metamagnetic instability. Spatial fluctuations of the local magnetic susceptibility in the alloys lead to a development of a partially ordered magnetic ground state of the itinerant 3d electron system. This results in a strong increase of the residual resistivity and a suppression of the temperature-dependent resistivity. Thermopower exhibits a complex temperature variation in both the magnetically ordered and in the paramagnetic state. This complex temperature variation is referred to the electronic density of states features in vicinity of Fermi energy and to the interplay of magnetic and impurity scattering. Our results indicate that the magnetic enhancement of the Co 3d-band in RCo$_{\rm 2}$--based alloys upon a substitution of Co by non-magnetic elements is mainly related to a progressive localization of the Co -- 3d electrons caused by disorder. We show that the magnitude of the resistivity jump at the Curie temperature for RCo$_{\rm 2}$ compounds exhibiting a first order phase transition is a non-monotonic function of the Curie temperature due to a saturation of the 3d--band spin fluctuation magnitude at high temperatures.