Magnetic structure of divalent europium compound EuGa${}_4$ studied by single crystal time-of-flight neutron diffraction

The magnetic structure of the intermetallic compound EuGa${}_4$ was investigated using single-crystal neutron diffraction with the time-of-flight (TOF) Laue technique on the new diffractometer SENJU at MLF of J-PARC. In spite of high neutron absorption of Eu, a vast number of diffraction spots were observed without isotope enrichment. The magnetic reflections were appeared at the positions with the diffraction indices of $h+k+l\mathrm{\ne }2n$ below 16 K, indicating that the ordering vector is $\mathbf{q}=(000)$. Continuous evolution of magnetic reflection intensity below $T_{\mathrm{N}}$ follows a squared Brillouin function for $S$=7/2. By adopting a wavelength-dependent absorption collection, the magnetic structure of EuGa${}_4$ was revealed that a nearly full magnetic moment of 6.4${\mu }_{\mathrm{B}}$ of Eu lies within the basal plane of the lattice. The present study reveals a well-localized divalent Eu magnetism in EuGa${}_4$ and demonstrates a high ability of SENJU to investigate materials with high neutron absorption.