Electron spin resonance and relaxation studies of double-layered manganites

Simon, F [Simon, Ferenc (Szilárdtestfizika), szerző] Fizika Tanszék (BME / TTK / FI); Atsarkin, VA; Demidov, VV; Gaal, R; Moritomo, Y; Miljak, M; Janossy, A [Jánossy, András (Szilárdtestfizika), szerző] Fizika Tanszék (BME / TTK / FI); Forro, L

Angol nyelvű Szakcikk (Folyóiratcikk) Tudományos
  • SJR Scopus - Condensed Matter Physics: D1
  • Fizika
Electronic properties of La2-2xSr1+2xMn2O7 (x=0.4 and 0.5) single crystals are studied by electron spin resonance (ESR) and spin-lattice relaxation time measurements. Spin susceptibility chi(T) determined from the ESR signal intensity and macroscopically measured static-susceptibility data are in good agreement, thus ESR detects all spin species in the system. In both compounds, the ESR spectra contain a single, nearly isotropic Lorentzian line associated with the exchange coupled Mn3+ and Mn4+ ions. For the x=0.5 compound, the fingerprints of charge ordering (CO) transition at T-CO=226 K are detected. In addition, strongly anisotropic ferromagnetic resonance spectra are found in both materials, suggesting the presence of extrinsic ferromagnetic phases. For x=0.4, the longitudinal relaxation time T-1 and the transversal relaxation time T-2 are equal around room temperature that is a sign of exchange narrowing. The T-1/T-2 ratio increases to about 5 approaching the Curie temperature T-C=126 K. No sign of critical speeding up of T-1 is detected. Instead, the slowing down of the relaxation rate takes place and T-1 is proportional to Tchi(T). This is attributed to the freezing of short-range magnetic correlations in the external field.
Hivatkozás stílusok: IEEEACMAPAChicagoHarvardCSLMásolásNyomtatás
2023-03-23 19:17