Mössbauer study of Nd2Fe14−xSixB compounds

Kowałczyk, A.; Stefański, P.; Budzyński, M.

doi:10.1002/pssa.2211390238

Cited by 4 publications

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“…The number of R neighbors of T atoms, ZCoR, amounts to 3.5-4 in these compounds.The values of TC,T'C and SC. are taken from [8,9]. The value of the JGdCo equals -11.5 K, -15 K and -20.9 K for RCo5, RCo4B and R3Co11B4, respectively.…”

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confidence: 99%

Magnetic Anisotropy and Exchange Interactions in R_n+1Co_3n+5B₂n Compounds

Kowałczyk

1994

Acta Phys. Pol. A

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The individual Co site contributions to the magnetocrystalline anisotropy in RCo5, RCo4 B and R3Co11B4 compounds have been studied. An analysis is given of the room temperature anisotropy constants of these compounds by using a model of Streever. The values of the rare earth-transition metal exchange coupling JRco/kB derived by mean field analysis of the Curie temperatures are -11.2 K, -i5 K and -20.9 K, respectively. In general, a decrease in JRco/kB with increasing Co concentration is observed.PACS numbers: 75.30.Gw, 75.30.Et IntroductionThe Rn+1CO3n+5B2n type compounds formed between rare earth (R), cobalt and boron are an important and physically interesting class of materials. Compounds in this series are known to exist for n = O (RCo5), n = 1 (RCo4B), n = 2 (R3Co11B4), n = 3 (R2Co7B3) and for n -f co (RCo3B2). These structures are based on the well-known CaCu5 structure. The unit cells are formed by alternative stacking of one layer of RCo5 and n layers of RCo3B 2 unit cells. They all have the hexagonal symmetry and belong to the space group of P 6 / m m m [1]. These compounds exhibit a strong axial anisotropy for R = Sm [2]. Smit et al. [3] determined the crystal field parameters by measuring Mössbauer spectrum of Gdn+1Co3n+5B2n compounds. The strength of the individual contributions to the magnetic anisotropy and magnetic moments of the non-equivalent Co sites in these compounds was studied using nuclear magnetic resonance (NMR) [4,5] and neutron diffraction [6].In the present investigation, the results of magnetocrystalline anisotropy and exchange interactions study of the RCo5, RCo4B and R3Co11B4 compounds are presented. A model proposed by Streever [4] is used to analyse the room temperature anisotropy constants of these compounds.

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Section: Resultsmentioning

confidence: 99%

Magnetic Anisotropy and Exchange Interactions in R_n+1Co_3n+5B₂n Compounds

Kowałczyk

1994

Acta Phys. Pol. A

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“…The Jcoco for Y,Co,,B, is 3.33 x lo-'' J. The 4f-3d exchange constant is much smaller and equals to about J,,,,/k, = 2.88 x lo-" J [9]. The saturation magnetization, M,, of 4.73pB/f.u.…”

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Magnetization in Y₃Co₁₁B₄ and Related Compounds

Kowałczyk

1993

Physica Status Solidi (b)

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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.

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