Exotic (anti)ferromagnetism in single crystals ofPr6Ni2Si3

Abstract

The ternary intermetallic compound, ${\text{Pr}}_{6}{\text{Ni}}_{2}{\text{Si}}_{3}$, is a member of a structure series of compounds based on a triangular structure where the number of Pr atoms in the prism cross section can be systematically varied. ${\text{Pr}}_{6}{\text{Ni}}_{2}{\text{Si}}_{3}$ contains two distinct Pr lattice sites which result in complex interactions between the magnetic ions. Extensive measurements of specific heat and magnetization on single-crystal samples indicate that ${\text{Pr}}_{6}{\text{Ni}}_{2}{\text{Si}}_{3}$ orders with both a ferromagnet and an antiferromagnet component, with ordering temperatures of 39.6 and $\ensuremath{\sim}32\text{ }\text{K}$, respectively. The ferromagnetic component $\ensuremath{\parallel}$ $c$ axis is accompanied by a large hysteresis, and the antiferromagnetic component $\ensuremath{\perp}$ $c$ axis is accompanied by a spin-flop-type transition. More detailed measurements, of the vector magnetization, indicate that the ferromagnetic and the antiferromagnetic order appear independent of each other. These results not only clarify the behavior of ${\text{Pr}}_{6}{\text{Ni}}_{2}{\text{Si}}_{3}$ itself but also of the other members of the structure series, ${\text{Pr}}_{5}{\text{Ni}}_{2}{\text{Si}}_{3}$ and ${\text{Pr}}_{15}{\text{Ni}}_{7}{\text{Si}}_{10}$.