Magnetic structure of HoBe13 in an applied magnetic field

The magnetic structure of HoBe13 and its evolution under an applied magneti c field have been examined using neutron diffraction and bulk magnetization measurements on a single crystal. In the absence of an external field this cubic compound orders at T-N = 5.7(1)K into a regular helical magnetic str ucture with propagation vector k = [001/3]. Third order harmonics appear at 4.4(1) K and are attributed to a deformation of the helical structure belo w this temperature. When a magnetic field is applied along a [001] axis two magnetic transitions occur. First the magnetic domain with propagation vec tor parallel to the field is favored and, with the addition of the induced ferromagnetic component, by about 4 kG we have a single-domain conical stru cture, The surprising observation was that at higher fields (15 kG at 1.4 K ) the other two domains reappear and become the preferred ones. This reentr ant behavior is due to the change of the magnetic structure to a canted arr angement, involving a ferromagnetic component along the applied field and a transverse collinear antiferromagnetic component. When the magnetic field is applied along a [110] axis only one transition is observed from the heli cal to the conical structure. The magnetic phase diagram of HoBe13 has been constructed.