Effect of Lattice Distortions on the Magnetic Behaviour of Perovskite‐Type Manganites

Abstract

Some series of solid solutions with perovskite-type structure are synthesized and investigated, viz. the binary systems Ndl-,, Me,MnO, where Me = Ca2+, Sr2+, Ba2+, and the ternary systems (Bi1-.La,)o.5Cao.5MnO3 and Bio,5(Cal -.Me,)0.5MnO3 where Me = = Sr2+, Pb2+, Ba2+. Distortions from the cubic perovskite structure are detected at room and liquid nitrogen temperature. Magnetic measurements are made in the temperature interval 77 to 800 OK. For all the compounds, a correlation between lattice distortions and magnetic behaviour is observed; 1. cubic and slightly distorted compounds exhibits a pure ferromagnetism; 2. distortions from the cubic structure give reduced spontaneous moments and in some cases antiferromagnetism developes. The ferromagnetic nature of the Mn3+-02--Mn3+ and Mn3+-02--Mn4+ interactions which are found in the non-distorted compounds is interpreted according to the Goodenough-Kanamori rules assuming that the quasi-static hypothesis is satisfied. The lattice distortions observed are thought t o give rise to a static distortion in the Mn3+ ion environment and an ordering of covalent bonds. As a result, some part of exchange couplings becomes antiferromagnetic. The influence of tJhe decreased subtended angle in the Mn-02--Mn linkage is discussed. This angle decreases from 180" when the lattice becomes distorted and this fact disturbs the orbital orthogonality. This results in a n increase of the antiferromagnetic t2g-t,g interaction via a-bonding and in the occurence of the other superexchange antiferromagnetic interactions which couple both the eg and t2g orbitals and the t2g and tZg orbitals via n-bonding. The contribution of double exchange to the ferromagnetism of mixed manganites is believed to be not important.

Magnetoelectric Devices for Spintronics

“…From the connection between (a) the local structural distortion ( Jahn-Teller type), magnetism, or transport (73,74) and (b) the corresponding sensitivity of the electronic states and charge dynamics to carrier doping (75,76), a modulation of the magnetic properties can be anticipated from the changes in the metal-insulator transition temperature by the electric field obtained in standard field-effect-transistor devices (77,78) or in a nonvolatile way in FeFETs (79,80). This tuning is also expected from the electric field modulation of the resistance at room temperature (81).…”

Progress and prospect for high temperature single-phased magnetic ferroelectrics

“…The effect of lattice distortions on the magnetic behavior of perovskite-type manganites were ever extensively studied for the binary systems Nd 1−x M x MnO 3 , and the ternary systems (Bi 1−x La x ) 0.5 Ca 0.5 MnO 3 and Bi 0.5 (Ca 1−x M x ) 0.5 MnO 3 , where M = Ca 2+ , Sr 2+ , Ba 2+ , Pb 2+ [126][127][128] . There exists a correlation between lattice distortions and magnetic behavior: (i) cubic and slightly distorted compounds exhibit a pure ferromagnetism; (ii) distortions from the cubic structure give reduced spontaneous moments and in some cases antiferromagnetism develops.…”

Enhanced Ferromagnetic Insulating State In La[sub 0.85]Ca[sub 0.15]Mn[sub 1−x]Cr[sub x]O[sub 3] (0≤x≤0.1)

“…Physical properties of manganites depend on the strength of Mn 3+ -O-Mn 4+ network which indeed have been observed in La 1-x A x MnO 3 (A = Ca, Pb etc.) [2,3]. Evidences available so far establishes that our understanding of FMI state in lightly doped Ln 1íx A x MnO 3 (Ln = rare earth and A = Alkaline earth metals) manganites is not very clear.…”