The magnetic phase diagram of HoGe1−xSix studied by neutron diffraction and magnetic measurements

Several samples (0.2 ≤ x ≤ 1.0) of HoGe_1−xSi_x (CrB type) were studied over an extensive temperature range by neutron diffraction. The relative stability of the two existing magnetic structures with wave vectors and q_x 0 q_z] depends on both the temperature and composition. The corresponding stability regions are shown in a magnetic phase diagram. The Néel temperature T_N and the transition temperature T_ic between the lock-in structure and the incommensurate structure increase with silicon content. At T_ic the wave vector jumps from the value to the incommensurate value q_x 0 q_z]. With increasing temperature the q_x and q_z components show a linear decrease and increase, respectively. The transition at T_ic is most probably of first order. The magnetic moments of Ho are confined to a direction close to the c-axis (5–7°) over the whole temperature range and order with a pure sinus modulation between T_ic and T_N.