Spin dynamics in La1−xSrxCoO3

M. J.R. Hoch, P. L. Kuhns, W. G. Moulton, A. P. Reyes, J. Wu, C. Leighton

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Abstract

The spin dynamics of Sr-doped cobaltite La1−xSrxCoO3(x = 0.14 and x = 0.4) has been investigated in both zero magnetic field and high field by NMR. The results are consistent with microscopically phase-separated regions of ferromagnetic and nonferromagnetic materials. Nuclear spin-lattice and spin-spin relaxation in the ferromagnetic regions is attributed to fluctuating hyperfine fields produced by double exchange between Co ions. The linear temperature dependence of the correlation time, obtained from the data analysis, suggests that lattice excitations modify the double-exchange process as the temperature is raised. In the nonferromagnetic regions, a distribution of nuclear spin-lattice relaxation times is found. It is likely that low-frequency fluctuating localized moments, such as small spin clusters, in spin-glass regions provide the relaxation mechanism for both the spin-glass and low-spin(S = 0) regions. A simple model involving these ideas can account for the stretched exponential nuclear magnetization recovery in the nonferromagnetic regions, and permits an estimate to be made of the mean size of low-spin regions.

Original languageEnglish (US)
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume69
Issue number1
DOIs
StatePublished - Jan 30 2004

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Spin dynamics
Spin glass
spin dynamics
Spin-lattice relaxation
Relaxation time
Magnetization
Ion exchange
nuclear spin
spin glass
Nuclear magnetic resonance
Ions
Magnetic fields
Recovery
Temperature
ferromagnetic materials
spin-lattice relaxation
relaxation time
recovery
low frequencies
moments

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Spin dynamics in La1−xSrxCoO3. / Hoch, M. J.R.; Kuhns, P. L.; Moulton, W. G.; Reyes, A. P.; Wu, J.; Leighton, C.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 69, No. 1, 30.01.2004.

Research output: Contribution to journalArticle

Hoch, M. J.R. ; Kuhns, P. L. ; Moulton, W. G. ; Reyes, A. P. ; Wu, J. ; Leighton, C. / Spin dynamics in La1−xSrxCoO3. In: Physical Review B - Condensed Matter and Materials Physics. 2004 ; Vol. 69, No. 1.
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AU - Reyes, A. P.

AU - Wu, J.

AU - Leighton, C.

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N2 - The spin dynamics of Sr-doped cobaltite La1−xSrxCoO3(x = 0.14 and x = 0.4) has been investigated in both zero magnetic field and high field by NMR. The results are consistent with microscopically phase-separated regions of ferromagnetic and nonferromagnetic materials. Nuclear spin-lattice and spin-spin relaxation in the ferromagnetic regions is attributed to fluctuating hyperfine fields produced by double exchange between Co ions. The linear temperature dependence of the correlation time, obtained from the data analysis, suggests that lattice excitations modify the double-exchange process as the temperature is raised. In the nonferromagnetic regions, a distribution of nuclear spin-lattice relaxation times is found. It is likely that low-frequency fluctuating localized moments, such as small spin clusters, in spin-glass regions provide the relaxation mechanism for both the spin-glass and low-spin(S = 0) regions. A simple model involving these ideas can account for the stretched exponential nuclear magnetization recovery in the nonferromagnetic regions, and permits an estimate to be made of the mean size of low-spin regions.

AB - The spin dynamics of Sr-doped cobaltite La1−xSrxCoO3(x = 0.14 and x = 0.4) has been investigated in both zero magnetic field and high field by NMR. The results are consistent with microscopically phase-separated regions of ferromagnetic and nonferromagnetic materials. Nuclear spin-lattice and spin-spin relaxation in the ferromagnetic regions is attributed to fluctuating hyperfine fields produced by double exchange between Co ions. The linear temperature dependence of the correlation time, obtained from the data analysis, suggests that lattice excitations modify the double-exchange process as the temperature is raised. In the nonferromagnetic regions, a distribution of nuclear spin-lattice relaxation times is found. It is likely that low-frequency fluctuating localized moments, such as small spin clusters, in spin-glass regions provide the relaxation mechanism for both the spin-glass and low-spin(S = 0) regions. A simple model involving these ideas can account for the stretched exponential nuclear magnetization recovery in the nonferromagnetic regions, and permits an estimate to be made of the mean size of low-spin regions.

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