Effect of Sr doping on the magnetic exchange interactions in manganites

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.

arXiv comment19 pages, 2 tables, 8 figures

References in corpus (10)

• Colossal Magnetoresistant Materials: The Key Role of Phase Separation
• The new Cold Neutron Chopper Spectrometer at the Spallation Neutron Source - Design and Performance
• Magnetic Cluster Excitations
• Magnon Damping by magnon-phonon coupling in Manganese Perovskites
• Softening and Broadening of the Zone Boundary Magnons in Pr0.63Sr0.37MnO3
• Evolution of spin-wave excitations in ferromagnetic metallic manganites
• Fermi surface of the colossal magnetoresistance perovskite La_{0.7}Sr_{0.3}MnO_{3}
• Effect of oxygen isotope substitution and crystal micro-structure on magnetic ordering and phase separation in {$(\mathrm{L}{\mathrm{a}}_{1-\mathrm{y}}\mathrm{P}{\mathrm{r}}_{\mathrm{y}}{)}_{0.7}\mathrm{C}{\mathrm{a}}_{0.3}\mathrm{Mn}{\mathrm{O}}_3$}
• On the Extraction of Exchange Parameters in Transition-Metal Perovskites
• Ferromagnetic and antiferromagnetic dimer splittings in LaMn0.1Ga0.9O3

Cited by in corpus (1)

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