Magnetization in Y₃Co₁₁B₄ and Related Compounds

Abstract

IntroductionThe rare earth-transition metal intermetallic compounds are attracting great interest caused not only by their application as materials for permanent magnets but also as opportunities for extended studies of magnetic properties of the 3d and 4f elements.The crystallographic structure of the ternary R-Co-B system, i.e. compounds R,, , C O~~+ , B~, , , was originally investigated by Kuzma and Bilonizhko [l]. Compounds in this series are known to exist for n = 0 (RCo,), n = 1 (RCo,B), n = 2 (R,Co,,B,), n = 3 (R,Co,B,), and n + co (RCo,B,).The Y,Co,,B, borides crystallize in a hexagonal structure of Ce,Co, ,B, type, space group P6/mm [l]. In this structure, rare earth atoms are distributed on two different crystallographic sites (la, 2e), the cobalt atoms on three different positions (2c, 6i,, 6i2), and boron is located on one type of site.The earliest studies of the structural and magnetic properties of R,+ , C O ,~+ 5B2n (R = Sm, Gd) alloys have been carried out Elmasry and Stadelmaier [2] and Smit et al. [3]. Recent Mossbauer studies [3] on the Gd,+ ,Co,,+ ,BZn series have shown that boron increases significantly the rare earth sublattice anisotropy via an enhancement of the second-order crystal field parameter at the R sites. The strength of the individual contributions to the magnetic anisotropy of the non-equivalent cobalt sites in these compounds was thoroughly studied by several researches [4, 51. The compound Sm,Co, ,B,, which corresponds to the case of n = 2 in the above formula, has been reported by Gupta et al. [6], to have a huge anisotropy field of 175 kOe at 295 K.

Relation between crystal structure and physical properties of Rn+1M5+3nB2n phases

“…The degree of itinerancy of the 3d magnetism is also linearly dependant on reciprocal exchange fields. Another approach has been to correlate the transition metal magnetisation to the average magnetic valence [74,75]. However these interesting results have described the behaviour of the mean transition metal magnetisation.…”

The structural and magnetic properties of Yn+1Co3n+5B2ncompounds investigated by neutron diffraction

“…A large variety in the cobalt magnetic moment, depending on the crystal site, is predicted, as well as the disappearance of the magnetism for the cobalt atom in the YCo 3 B 2 compound. The evolution of the other magnetic characteristics, such as the exchange interactions [12], the magnetization [13] or the susceptibility [14], has also shown large changes upon substitution of boron for cobalt.…”