Electrical magnetotransport properties in RCo12B6 compounds ( R=Y , Gd, and Ho)

Abstract

Remarkable electronic transport and magnetotransport properties are found in the intermetallic compounds RCo 12 B 6 (R = Y, Ho, and Gd). Detailed resistivity, magnetoresistance, and Hall effect measurements are reported in the temperature range between 2 and 320 K under applied magnetic fields up to 9 T. Auxiliary magnetization results and structural data are also reported. The magnetic ordering observed in these systems depends on the rare-earth atom. In the YCo 12 B 6 compound, a ferromagnetic-type ordering is observed (T C ≈ 149 K) whereas the GdCo 12 B 6 and HoCo 12 B 6 compounds show ferrimagnetic-type ordering (T C ≈ 162 and 144 K, respectively) and their magnetization exhibits the compensation phenomenon. All compounds show high residual-resistance ratio (RRR) rates and resistivities typical of magnetically ordered systems, with a characteristic downward inflection at the critical temperature. The resistivity results are described in terms of the interplay between the electron-phonon interaction and a magnetic term. The magnetoresistance is consequence of a complex superposition of effects due to conduction in spin-polarized bands and to spin-disorder suppression. A strong positive contribution, which prevails at low temperatures, is described with a basis on the Campbell-Fert model that assumes conduction by two spin-polarized currents with a spin-mixing term. The usual negative effect related to suppression of spin disorder becomes the dominant contribution at intermediate-and high-temperature regimes. At low temperatures, the Hall resistivity results are also consistent with conduction by two spin-polarized bands. Moreover, a sign reversal observed in the Hall resistivity for all compounds at low temperatures indicates that the majority spin-up band is holelike, while the minority spin band is electronlike. The ordinary and anomalous Hall contributions could be separated. The intrinsic Karplus-Luttinger mechanism is the most relevant contribution to the anomalous Hall resistivity in all studied compounds. However, an additional term due to chiralities related to canting of the Co moments also plays a role in the temperature region near T C .

Exploring the Different Degrees of Magnetic Disorder in TbxR1−xCu2 Nanoparticle Alloys

“…Over the last few decades, the traditional noble metals have been replaced by magnetic Rare Earth (R) (e.g., RMn 2 [3]), opening up the possibility for the occurrence of more complex magnetic phenomena. These have been especially attractive for spintronics or magneto-optical recording applications (e.g., RCo 12 B 6 [4]). The situation becomes even more interesting when the 3d ion is non-magnetic (as in Cu [5] or Al [6]), as the starting magnetic ordered state can be tuned following two routes: on the one hand, one can modify the random-bond contribution by using 4 f ions as dopants [7,8].…”

Giant spontaneous resistivity jumps in La0.825Ce0.175Fe12B6

“…The intermetallic system LaFe12B6 is unique among the RT12B6 family in being an antiferromagnet with a magnetic transition temperature much smaller than the Curie point of the Co-based RCo12B6 ferro-(R =Y, La-Sm) or ferri-(R = Gd-Tm) magnets (TC =134 -162 K) 15 and an order of magnitude smaller when compared to the magnetic ordering temperature of any rare-earth iron-rich binary intermetallic. Interestingly, extraordinary magnetotransport effects have been most recently observed in RCo12B6 alloys with R = Y, Gd and Ho 16 .…”

Magnetic-field-induced avalanches in magnetization and magnetoresistance of La0.9Ce0.1Fe12B6 compound

“…The Néel temperature of LaFe12B6 is an order of magnitude smaller when compared to the magnetic transition temperature of any rare-earth iron-rich binary alloy. Extraordinary magnetotransport properties have been most recently reported in RCo12B6 intermetallics with R = Y, Gd and Ho [20].…”