Issues »  Volume 39, Issue 4

3d–4f-Intermetallides. Exchange and Anisotropy. Many-Electron Statistics

O. I. Mitsek, V. M. Pushkar

G.V. Kurdyumov Institute for Metal Physics, NAS of Ukraine, 36 Academician Vernadsky Blvd., UA-03680 Kyiv-142, Ukraine

Received: 13.03.2017. Download: PDF

Magnetic properties of the 3$d$(Fe)–4$f$(RE) intermetallides are calculated by introduction of both the many-electron operator spinors (MEOS) and the chemical-bonds’ fluctuations as MEOS Fourier images. Dependences of both the critical temperature $T_{\textrm{c}}$ and the compensation temperature $T_k$ on the rare-earth ion (REI) spin $S_f$($T$) are obtained. They agree with data for Fe$_2$RE and Fe$_3$RE. Axial symmetry of Nd$_2$Fe$_{14}$B is connected with orbital moment $L_r$ of the B$^5$ ion with inhomogeneous (covalent) B–Fe bond. Direct Fe–Fe exchange explains the dependence $T_{\textrm{c0}} \cong T_{\textrm{c}}$(Fe)$x^2_D$ on the concentration $x_D$ of Fe ions. Additional term ${\delta}T_{\textrm{c}} \propto S^2_f$ for Fe$_2$RE ferromagnets is given by direct Fe–RE exchange, and for ferrimagnets, it is conditioned by indirect antiferromagnetic RE–$e_{\textrm{g}}$–RE exchange. The magnetization ($M_s$) compensation temperature depends on the REI angular moment $J$. Analogous properties for Nd$_2$Fe$_{14}$B ferrimagnet (such as inflection of the $M_{s}(T)$ function, ferromagnetic anisotropy field $B_A \propto (1 + AT)^{-2}$, etc.) are obtained and agree with literature data.

Key words: REI–Fe intermetallides, many-electron operator spinors, theory of direct covalent ferromagnetic and indirect band-covalent antiferromagnetic exchange, uniaxial deformation, ferromagnetic anisotropy.

URL: http://mfint.imp.kiev.ua/en/abstract/v39/i04/0425.html

DOI: https://doi.org/10.15407/mfint.39.04.0425

PACS: 61.50.Ks, 71.20.Eh, 71.30.+h, 75.10.Dg, 75.30.Kz, 75.30.Mb

Citation: O. I. Mitsek and V. M. Pushkar, 3d–4f-Intermetallides. Exchange and Anisotropy. Many-Electron Statistics, Metallofiz. Noveishie Tekhnol., 39, No. 4: 425—439 (2017) (in Russian)

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