Electron spin resonance study of spin correlations in charge-ordered La2−2xSr1+2xMn2O7(x=0.6)

Abstract

Electron spin resonance (ESR) studies have been performed on a bilayered manganite La2−2xSr1+2xMn2O7(x=0.6) single crystal. The charge ordering (CO) and antiferromagnetic (AFM) transitions can be well identified from the ESR spectra in both the ab plane and c axis directions. A coexistence of paramagnetic resonance signal and low-field AFM resonance signal was observed below the CO temperature TCO. The analysis of the ESR parameters as a function of temperature suggests the existence of weak ferromagnetic (FM) correlations in the paramagnetic state and AFM correlations below TCO. The competition of FM and AFM correlations results in a broad peak in ESR intensity. Our results also show that the intensity of AFM correlations increases with decreasing temperature as the system enters from the CO state into the A-type AFM ground state. Therefore, the evolution and anisotropy of spin correlations can be fully mapped by ESR study.

Effects of pH and sintering temperature on the synthesis and electrical properties of the bilayered LaSr2Mn2O7 manganite prepared by the sol–gel process

“…In the LaSr 2 Mn 2 O 7 compound, the A-type AFM order and CE-type charge ordering have been observed experimentally around T N,CO CE & 210 K, and then another transition to CE-type charge and spin-ordered states below T N,CO A & 145 K [9]. Various methods have been used to synthesize bilayered manganites including floating zone methods for single crystal growth [10,11], conventional solid-state reaction for polycrystalline compounds [12,13], pulse laser deposition technique for thin film structures, [14,15], and sol-gel processes [16][17][18]. The bilayered polycrystalline specimens are commonly prepared by the solid-state reaction method, which requires high sintering temperature (typically *1673 K or higher) for more than 20 h with 3-4 times intermediate grindings [12,13,19] to make singlephase structures.…”

Competition of spin states in heterogenous LaMnO3+δ

“…Among a few, ESR is a very sensitive probe to the local spin interactions and has been proved to be powerful to investigate the short range spin interactions in manganites. 10,11) In LaMnO 3+¤ , ESR has been used to measure the contribution of JT distortion at high temperature 12) and magnetic phase separation in nanocrystals. 13) We therefore use ESR to study the heterogeneous spin states of LaMnO 3+¤ at low temperature, especially for that with low and high ¤ values.…”