Effect of Sr doping on the magnetic exchange interactions in manganites of type $\mathrm{L}{\mathrm{a}}_{1-x}\mathrm{S}{\mathrm{r}}_x\mathrm{M}{\mathrm{n}}_y{A}_{1-y}{\mathrm{O}}_3(A=\mathrm{Ga},\mathrm{Ti};0.1\le y\le 1)$

Journal Article · 14 March 2017 · Physical Review B

DOI: https://doi.org/10.1103/PhysRevB.95.104414 · OSTI ID:1360072

Furrer, Albert ^[1]; Podlesnyak, Andrey A. ^[2]; Pomjakushina, Ekaterina ^[3]; Pomjakushin, Vladimir ^[4]

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1. Paul Scherrer Inst. (PSI), Villigen (Switzerland). Lab of Neutron Scattering and Imaging; SwissNeutronics AG, Klingnau (Switzerland)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division
3. Paul Scherrer Inst. (PSI), Villigen (Switzerland). Lab. for Scientific Developments and Novel Materials
4. Paul Scherrer Inst. (PSI), Villigen (Switzerland). Lab of Neutron Scattering and Imaging

Strontium doping transforms manganites of type La _{1 - x} Sr _x Mn O ₃ from an insulating antiferromagnet ( x = 0 ) to a metallic ferromagnet ( x > 0.16 ) due to the induced charge carriers (holes). We employed neutron scattering experiments in order to investigate the effect of Sr doping on a tailor-made compound of composition La _0.7 S r _0.3 M n _0.1 Ti _0.3 G a _0.6 O ₃ . By the simultaneous doping with S r ^{2 +} and Ti ^{4 +} 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 T _C = 215 K , there is a first-order reconstructive phase transition from the trigonal R - 3 c structure to the orthorhombic Pnma structure via an intermediate virtual configuration described by the common monoclinic subgroup P2 ₁ / c . The magnetic excitations associated with Mn ^{3 +} dimers give evidence for two different nearest-neighbor ferromagnetic exchange interactions, in contrast to the undoped compound LaM n _y A _{1 - y} O ₃ where both ferromagnetic and antiferromagnetic interactions are present. Furthemore, 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. Here, 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.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1360072
• Alternate ID(s): OSTI ID: 1347051
• Journal Information: Physical Review B, Vol. 95, Issue 10; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English