Yu.S. Orlov†a,b,
S.V. Nikolaev‡a,b,
V.A. Dudnikov§a,
V.A. Gavrichkov*a,
S.G. Ovchinnikov#a,b aKirensky Institute of Physics, Federal Research Center Krasnoyarsk Science Center of the Siberian Branch of the Russian Academy of Sciences, Academgorodok 50, str. 38, Krasnoyarsk, 660036, Russian Federation bSiberian Federal University, pr. Svobodnyi 79, Krasnoyarsk, 660041, Russian Federation
We present experimental and theoretical results of spin crossover studies in magnetically ordered materials. The effect of spin crossovers on the electronic structure of transition metal oxides and on the Bose condensation of spin excitons in the vicinity of the spin crossover is considered. A new method for calculating the interatomic superexchange interaction in transition metal oxides is discussed that allows considering selective contributions of excited magnetic cation terms. Changes in the exchange interaction sign are predicted for spin crossovers for d5—d7 ions. In the RCoO3 family of rare-earth cobaltites, the ground state is nonmagnetic, but, as the temperature increases, thermal excitations of high-spin states give rise to a number of experimentally detectable features. In defective RCoO3 samples, stabilization of the high-spin term and ferromagnetic ordering are possible. Dynamical crossovers under external pumping and the dynamics of multiplicity, magnetization, and local lattice distortions are discussed. Geophysical implications of spin crossovers are considered, and metallic properties of Earth's mantle at a depth of 1400—1800 km are predicted.
Keywords: spin crossovers, exchange interaction, Bose condensation, spin excitons, transition metal oxides, rare earth cobaltites, strong electron correlations, antiferromagnetism, ferromagnetism, metal—insulator transition, Earth's mantle, Hubbard model PACS:71.30.+h, 75.30.Cr, 75.30.Et, 75.47.Lx, 75.50.Pp (all) DOI:10.3367/UFNe.2022.05.039195 URL: https://ufn.ru/en/articles/2023/7/a/ 001097028100001 2-s2.0-85182909997 2023PhyU...66..647O Citation: Orlov Yu S, Nikolaev S V, Dudnikov V A, Gavrichkov V A, Ovchinnikov S G "Features of spin crossovers in magnetic materials" Phys. Usp.66 647–672 (2023)
Sviridov D T, Smirnov Yu F Teoriya Opticheskikh Spektrov Ionov Perekhodnykh Metallov (Theory Of Optical Spectra Of Transition Metal Ions) (Moscow: Nauka, 1977)
Bersuker I B Elektronnoe Stroenie I Svoistva Koordinatsionnykh Soedinenii. Vvedenie V Teoriyu (Electronic Structure And Properties Of Coordination Compounds. Introduction To Theory) (Leningrad: Khimiya, 1976)
Nesterov A I, Ovchinnikov S G JETP Lett.90 530 (2009); Nesterov A I, Ovchinnikov S G Pis’ma Zh. Eksp. Teor. Fiz.90 580 (2009)
Pavarini E et al (Eds) The LDA+DMFT Approach To Strongly Correlated Materials. German Research School For Simulation Sciences(Reihe Modeling and Simulation) Vol. 1 (Jülich: Forschungszentrum. German Research School for Simulation Sciences GmbH, 2011)
Irkhin V Yu, Irkhin Yu P Electronic Structure, Correlation Effects And Physical Properties Of D - And F -Metals And Their Compounds (Cambridge: Cambridge Intern. Sc. Publ., 2007); Translated from Russian, Irkhin V Yu, Irkhin Yu P Elektronnaya Struktura, Korrelyatsionnye Effekty I Fizicheskie Svoistva D - I F -perekhodnykh Metallov I Ikh Soedinenii 2nd ed., correct. and enlarg. (Moscow-Izhevsk: RKhD, Inst. Komp. Issled., 2008)
Gavrichkov V A, Ovchinnikov S G, Yakimov L E J. Exp. Theor. Phys.102 972 (2006); Gavrichkov V A, Ovchinnikov S G, Yakimov L E Zh. Eksp. Teor. Fiz.129 1103 (2006)
Irkhin V Yu, Katsnel’son M I, Trefilov A V J. Exp. Theor. Phys.78 936 (1994); Irkhin V Yu, Katsnel’son M I, Trefilov A V Zh. Eksp. Teor. Fiz.105 1733 (1994)
Gavriliuk A G et al JETP Lett.84 161 (2006); Gavriliuk A G et al Pis’ma Zh. Eksp. Teor. Fiz.84 190 (2006)
Kantor I Yu, Dubrovinsky L S, McCammon C A Proc. of the Joint 20th AIPART — 43rd EHPRG, Intern. Conf. on High Pressure Science and Technology, June 27 - July 1, 2005, Karlsruhe, Germany (Eds E Dinjus, N Dahmen) (Karlsruhe: Forschungszentrum Karlsruhe, 2005), T5-P101