Irreversible field-induced magnetic phase transitions and properties of Ho3Co

• Published in: Journal of physics. Condensed matter 2005-06, Vol.17 (21), p.3445-3462
• Main Authors: Baranov, N V, Goto, T, Hilscher, G, Markin, P E, Michor, H, Mushnikov, N V, Parks, J-G, Yermakov, A A
• Format: Article
• Language: English
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/17/21/034

The results of magnetic susceptibility, magnetization, electrical resistivity and specific heat measurements performed on Ho3Co single crystals show that this compound exhibits two different antiferromagnetic structures: AFII at 8 K < T < 22 K and AFI below Tt = K. Below the Ndel temperature TN = 22 K the application of a magnetic field along the main crystallographic directions induces magnetic phase transitions which are accompanied by giant magnetoresistance. At T < Tt the field-induced phase transitions along the c- and b-axes are found to be irreversible, and a small ferromagnetic component is observed along the a-axis. These peculiarities are associated with the non-Kramers character of the Ho ion and with the presence of a complex incommensurate magnetic structure of Ho3Co below TN. The temperature coefficient of the electrical resistivity for Ho3Co above TN over a wide temperature range is found to differ from that observed for other R3Co compounds. Such a behaviour is attributed to the presence of an additional contribution to the conduction electron scattering by spin fluctuations induced by f-d exchange in the itinerant d-electron subsystem. The value of this extra contribution and its temperature range is suggested to depend on the spin value of the R ion. The excess of the effective magnetic moment per R ion, which is observed in Ho3Co and in other R3M type compounds, is also attributed to spin fluctuations induced by f-d exchange.