Abstract
We have studied successive magnetic transitions of HoCoGa5 at TN1 = 9.6 K and TN2 = 7.5 K
by using powder neutron diffraction. Apparent superlattice peaks were observed at temperatures
below TN1. With further decreases temperature, the patterns exhibit a substantial change at temperatures
below TN2. The observed magnetic peaks at 8 K (AntiFerromagnetic InCommensurate
(AFIC) phase : TN2 < T < TN1) can be represented by the propagation vector qL = (1/2 0 ) with
= 0.35(2). In contrast, the magnetic structure becomes commensurate with qC = (1/2 0 1/2) at
4 K (AntiFerromagnetic Commensurate (AFC) phase : T < TN2). The temperature dependence of
magnetic intensity shows an apparent temperature hysteresis at TN2, indicates a first-order transition
at TN2. Analysis of the integrated intensity at 4 K reveals that the Ho moment with a size
of 8.6(2) μB, oriented parallel to the c-axis in the AFC phase. While the successive transitions
of HoCoGa5 are different from those of TbCoGa5, the magnetic structure in the AFC phase of
HoCoGa5 is the same as the AFTb
I of TbCoGa5, and may indicate an additional transition at a
lower temperature in HoCoGa5.
