Magnetic and electronic properties of La₃ MO₇ and possible polaron formation in hole-doped La₃ MO₇ (M  =  Ru and Os)

Abstract

Abstract. Oxides with 4d/5d transition metal ions are physically interesting for their particular crystalline structures as well as the spin-orbit coupled electronic structures. Recent experiments revealed a series of 4d/5d transition metal oxides R 3 M O 7 (R: rare earth; M : 4d/5d transition metal) with unique quasi-one-dimensional M chains. Here first-principles calculations have been performed to study the electronic structures of La 3 OsO 7 and La 3 RuO 7 . Our study confirm both of them to be Mott insulating antiferromagnets with identical magnetic order. The reduced magnetic moments, which are much smaller than the expected value for ideal high-spin state (3 t 2g orbitals occupied), are attributed to the strong p − d hybridization with oxygen ions, instead of the spin-orbit coupling. The Ca-doping to La 3 OsO 7 and La 3 RuO 7 can not only modulate the nominal carrier density but also affect the orbital order as well as the local distortions. The Coulombic attraction and particular orbital order would prefer to form polarons, which might explain the puzzling insulating behavior of doped 5d transition metal oxides. In addition, our calculation predict that the Ca-doping can trigger ferromagnetism in La 3 RuO 7 but not in La 3 OsO 7 .

Magnetic and electronic properties of La-doped hexagonal 4H-SrMnO3

“…Considering the results of electron restricted by strong Coulombic interaction and the lattice distortions in this system, the 3d polaron is formed, which will enhance the nearestneighbor magnetic coupling and contribute to the semiconductor behavior. [9] Similar magnetic polarons also exist in the electron-doped manganite La x Ca 1−x MnO 3 , which are Mnsites FM clusters embedded in AFM region. [40] Based on the polaron forming and antiferromagnetic arrangement between Mn 3 -Mn 4 dimer and Mn 1 -Mn 2 dimer, a nonzero net magnetic moment appears.…”

“…[1][2][3] To achieve this goal, two conditions need to be met: (i) effective modulation method, and (ii) ideal material platform. Firstly, in terms of regulation methods, a frequently used approach is doping, which can be realized through oxygen deficiency, [4][5][6] cation substitution, [7][8][9][10] and interfacial charge transfer. [11][12][13][14] Via proper doping, one can engineer exciting physical phenomena in a new dimension, [15,16] such as magnetic phase transition and insulator-metal transition (or even insulator-superconductor transition).…”