Influence of Ni substitution on the phase transitions and magnetocaloric effect of NdCo2 at cryogenic temperatures

TL;DR

This study explores how partial Ni substitution in NdCo2 affects its structural phase transitions and magnetocaloric properties at cryogenic temperatures, revealing shifts in transition temperatures and a decrease in magnetic moment.

Contribution

It provides new insights into the impact of Ni substitution on phase transitions and magnetocaloric effects in NdCo2 compounds, combining neutron diffraction and magnetization measurements.

Findings

Transition temperatures decrease with Ni content

Orthorhombic phase is suppressed for x >= 0.5

Magnetocaloric effect diminishes with Ni substitution

Abstract

We have investigated NdCo2-xNix cubic Laves compounds with 0 <= x <= 1 using neutron diffraction and bulk magnetization measurements to study the influence of partial Ni substitutions of Co on the phase transitions and the magnetocaloric effect. Upon cooling, NdCo2 undergoes a cubic to tetragonal transition at 100 K, and a tetragonal to orthorhombic transition at 42 K. The transitions are associated with long-range ferromagnetic ordering of the magnetic moments along the c axis and spin reorientation into the ab plane, respectively. Both transitions shift to lower temperatures as the Ni content x increases. For x >= 0.5, the orthorhombic phase is suppressed. Additionally, there was a reduction in the magnetic moment upon increasing the Ni substitution of Co. The magnetocaloric effect was determined both indirectly and directly, with good agreement between the methods. NdCo2 exhibits an adiabatic temperature change of 6.3 K for a field of 20 T, which is decreased to 4.9 K for NdCoNi for the same field strength due to the reduced magnetic moment upon Ni substitution.