First-order transition in the weak ferromagnetic state ofErNi2B112C

Abstract

A detailed investigation of the ordering process of a weak ferromagnetic state in superconducting ${\text{ErNi}}_{2}{^{11}\text{B}}_{2}\text{C}$ was made by a neutron-diffraction technique. The results reveal that there are at least two magnetic phase transitions around $\ensuremath{\sim}2.3\text{ }\text{K}$ related to a weak ferromagnetic ordering process. We conclude that one of the two transitions is of the first order and corresponds to a rotation of spins from the $a$ to the $b$ axis. Details of the spin arrangements in a weak ferromagnetic state were also reconsidered. The data reveal that clear magnetic peaks appear at $\mathbit{Q}$ positions with $\mathbit{q}=(1\text{ }0\text{ }0)$ in the weak ferromagnetic state, which are prohibited by extinction rules in the model proposed by Jensen [Phys. Rev. B 65, 140514 (2002)].