Magnetic properties and magnetic structure of the Mn5Si3-type Tb5Si3 compound

Neutron diffraction and magnetization measurements have been performed on the Tb5Si3 compound (hexagonal Mn5Si3-type, hP16, P6(3)/MCM) to understand its magnetic structure and magnetic properties. The temperature-dependent neutron diffraction results prove that this intermetallic phase shows a complex flat spiral magnetic ordering, presenting three subsequent changes in magnetization at T-m1(Neu) similar to 100 K, T-m2(Neu) = 62(4) K and T-m3(Neu) = 54(4) K on cooling. However, the magnetization data depict two transitions at 72 K (T-N1) and 55 K (T-N2). The extended temperature range between T-m1(Neu) and T-m2(Neu) over which the neutron diffraction patterns slowly evolve might correspond to the high-temperature anti ferromagnetic transition at T-N1 and low-temperature antiferromagnetic transition at T-N2 of the magnetic data. Between T-m1(Neu) similar to 100k and T-m2(Neu) = 62(4)KTb5Si3 shows a flat spiral antiferromagnetic ordering with a propagation vector K-1 = [0,0, +/- 1/4]; then, between T-m2(Neu) = 62(4) K and T-m3(Neu) = 54(4) K the flat spiral type ordering is conserved, but by two coexisting propagation vectors K-1 = [0,0, +/- 1 /4] and K-2 = [0,0, +/- 0.4644(3)]. The terbium magnetic moments arrange in the XY(ab) plane of the unit cell. Below T-m3(Neu) = 54(4) K the magnetic component with K-1 = [0,0, +/- 1/4] vanishes and magnetic structure of Tb5Si3 is a flat spiral with K-2 = [0,0, +/- 0.4644(3)], only. Low field magnetization measurements confirm the occurrence of complex, multiple magnetic transitions. The field dependence of the magnetization indicates a metamagnetic transition at a critical field of similar to 3T. (C) 2008 Elsevier B.V. All rights reserved.