Irreversible field-induced magnetic phase transitions and properties of Ho₃Co

Abstract

The results of magnetic susceptibility, magnetization, electrical resistivity and specific heat measurements performed on Ho 3 Co single crystals show that this compound exhibits two different antiferromagnetic structures: AF II at 8 K < T < 22 K and AF I below T t ≈ 8 K. Below the Néel temperature T N = 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 < T t 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 Ho 3 Co below T N . The temperature coefficient of the electrical resistivity for Ho 3 Co above T N over a wide temperature range is found to differ from that observed for other R 3 Co 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 Ho 3 Co and in other R 3 M type compounds, is also attributed to spin fluctuations induced by f-d exchange.

Field-induced magnetic phase transitions and metastable states in Tb3Ni

“…ate ferrimagnetic-type state (IFIM) to the forced ferromagnetic (FM) state. A similar magnetoresistance upon application of external magnetic field was previously reported for numerous binary rare-earth intermetallic compounds [10,11,27,39,51]. A substantial hysteresis of ∆ρ(H)/ρ(0) vs H curves measured on magnetization and demagnetization persists in a wide magnetic field range below H up C2 .…”

“…The deviation from the CW law and an additional contribution to the effective magnetic moment arise from the enhanced short-range magnetic order persisting in Tb 3 Ni over a wide temperature range up to 5-6 T N [6]. Similar behavior was previously reported for other binary intermetallic compounds with high content of rare-earth metal such as R 3 T [13,25,27], R 5 Pd 2 [33] and R 7 Rh 3 [34,35]. Moreover, the contribution from spin-fluctuations in the d-electron subsystem may affect the susceptibility behavior as well [23,26].…”

“…Magnetoelastic interactions along with the strong magnetocrystalline anisotropy and competing exchange interactions seem to be crucial for stabilizing the forced ferromagnetic state after removal of an external magnetic field [62]. It is worth to mention, that irreversibilities in the magnetization behavior and the formation of metastable field-induced states were observed in other R 3 T type compounds (Dy 3 Co [63], Ho 3 Co [27]) as well as in some other highly-anisotropic antiferromagnets [64,65].…”

“…Particularly, spin-fluctuations were suggested to be responsible for an enhanced value of the T -linear specific heat coefficient (γ = 118 mJ mol −1 K −2 for Gd 3 Rh [23] and γ = 86 mJ mol −1 K −2 for Gd 3 Ni [24]) as well as for the tendency to saturation of the electrical resistivity in paramagnetic state [25,26]. The saturation of the resistivity observed in numerous R 3 T compounds was also ascribed to the short-range magnetic order persisting up to temperatures well above Néel temperature and s-d scattering mechanism [6,27]. The complex multi-component incommensurate magnetic structures observed in R 3 T with non-Kramers R ion apparently arise from the competition of exchange interactions of different types and lowsymmetry crystal electric field [6,[12][13][14][15].…”

Comprehensive study of the magnetic phase transitions in Tb3Co combining thermal, magnetic and neutron diffraction measurements

“…Several studies have already been undertaken for R 3 Co with different R such as Gd [6][7][8][9][10][11], Ho [9,12], Er [9,11,[13][14], Dy [11,[15][16][17][18][19], and Tb [9,11,[20][21][22][23][24]. In this particular work, we are focusing on Tb 3 Co as it presents quite a complex behavior and there are several issues not studied or resolved yet.…”