Abstract
Strontium doping transforms manganites of type La1-xSrxMnO3 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 La0.7Sr0.3Mn0.1Ti0.3Ga0.6O3. 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=215K, 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 LaMnyA1-yO3 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.
Original language | English |
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Article number | 104414 |
Journal | Physical Review B |
Volume | 95 |
Issue number | 10 |
DOIs | |
State | Published - Mar 14 2017 |
Funding
Part of this paper was completed at SINQ, Villigen PSI, Switzerland. Research at the Oak Ridge National Laboratory Spallation Neutron Source was supported by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.