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arXiv · 1702.06802

Effect of Sr doping on the magnetic exchange interactions in manganites

A. Furrer·A. Podlesnyak·E. Pomjakushina·V. Pomjakushin
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Abstract

Strontium doping transforms manganites of type La(1-x)Sr(x)MnO(3) from an insulating antiferromagnet (x=0) to a metallic ferromagnet (x>0.16) due to the induced charge carriers (holes). Neutron scattering experiments were employed to investigate the effect of Sr doping on a tailor-made compound of composition La(0.7)Sr(0.3)Mn(0.1)Ti(0.3)Ga(0.6)O(3). By the simultaneous doping with Sr2+ and Ti4+ ions the compound remains in the insulating state, so that the magnetic interactions for large Sr doping can be studied in the absence of charge carriers. At TC=215 K there is a first-order reconstructive phase transition from the trigonal R-3c structure to the orthorhombic Pnma structure via an intermediate virtual configuration described by the common monoclinic subgroup P21/c. The magnetic excitations associated with Mn3+ dimers give evidence for two different nearest-neighbor ferromagnetic exchange interactions, in contrast to the undoped compound LaMnyA(1-y)O(3) where both ferromagnetic and antiferromagnetic interactions are present. The doping induced changes of the exchange coupling originates from different Mn-O-Mn bond angles determined by neutron diffraction. The large fourth-nearest-neighbor interaction found for metallic manganites is absent in the insulating state. We argue that the Ruderman-Kittel-Kasuya-Yosida interaction reasonably accounts for all the exchange couplings derived from the spin-wave dispersion in metallic manganites.

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A. Furrer, A. Podlesnyak, E. Pomjakushina, V. Pomjakushin. 2017-02-22. Effect of Sr doping on the magnetic exchange interactions in manganites. https://doi.org/10.1103/physrevb.95.104414

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