Neutron-diffraction study of the evolution of antiferromagnetic order in UPt3 doped with Pd

TL;DR

This neutron-diffraction study investigates how antiferromagnetic order in UPt3 evolves with Pd doping, revealing persistent small-moment order at low doping and a transition to a large-moment phase at higher doping levels.

Contribution

The paper provides detailed experimental insights into the evolution of antiferromagnetic phases in UPt3 with Pd doping, highlighting the coexistence and transition between small-moment and large-moment antiferromagnetic orders.

Findings

Small-moment antiferromagnetic order persists up to x=0.005 doping.

Large-moment antiferromagnetic phase appears at x>=0.01.

Neel temperature remains approximately 6 K for small moments, peaks at 5.8 K for large moments.

Abstract

Neutron-diffraction experiments have been carried out on U(Pt1-xPdx)3 single crystals (x<= 0.05). The small-moment antiferromagnetic order (SMAF) reported for pure UPt3 is robust upon doping and persists till at least x= 0.005. The ordered moment grows from 0.018(2) mB/U-atom for pure UPt3 to 0.048(8) mB/U-atom for x= 0.005. The Neel temperature, TN, is approximately 6 K and does not vary with Pd contents. The order parameter for the SMAF has an unusual quasi-linear temperature variation. For x>= 0.01 a large moment antiferromagnetic phase (LMAF) is found. For this phase at optimum doping (x= 0.05) TN attains a maximum value of 5.8 K and the ordered moment equals 0.63(5) mB/U-atom. TN(x) for the LMAF follows a Doniach-type phase diagram. We infer that the antiferromagnetic instability in U(Pt1-xPdx)3 is located in the range 0.5-1 at.% Pd.