33S NMR Measurements in 33S-enriched Ferromagnetic EuS and the Question of Power-law Behaviors

In order to resolve two previous conflicting reports on detectable but weak nuclear magnetic resonance (NMR) 33S signals in unenriched EuS, a sample of 33S-enriched EuS was prepared and the NMR and its temperature dependence were measured in the range from 1.3 to 4.2 K. It was verified that the T=0 extrapolated NMR signal has a value of 12.73 MHz (≈ 39 kG), not 5.4 MHz, as one group had reported. The temperature dependence of the NMR was used to assess the applicability of two proposed spin-wave-region power-law schemes. The schemes attempted to systematize and explain the simple power-law behaviors measured by NMR and other techniques that have been reported (or have been present in measured data, but not reported) for more than five decades. The scheme proposed by Koebler et al. [Physica B 364, 55 (2005)] contends that the low-temperature magnetization of EuS follows a simple T2 behavior all the way up to 0.75Tc. The 33S spin-echo measurements are consistent with a power law, but cast doubt on the T2 dependence. Possible reasons for discrepancies between various EuS NMR measurements are discussed in the paper as well as means of resolving such issues by future experiments. Disciplines Physical Sciences and Mathematics | Physics Comments Suggested Citation: Bykovetz, N., J. Klein, and C.L. Lin. (2009). "33S NMR measurements in 33S-enriched ferromagnetic EuS and the question of power-law behaviors." Journal of Applied Physics. 105, 07E103. © 2009 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Applied Physics and may be found at http://dx.doi.org/10.1063/1.3055270. This journal article is available at ScholarlyCommons: http://repository.upenn.edu/physics_papers/79 S NMR measurements in S-enriched ferromagnetic EuS and the question of power-law behaviors N. Bykovetz, J. Klein, and C. L. Lin Department of the Army, CECOM LCMC, AMSEL-SF-R, Fort Monmouth, New Jersey 07703-5024, USA Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6396, USA Department of Physics, Temple University, Philadelphia, Pennsylvania 19122-6082, USA Presented 14 November 2008; received 21 September 2008; accepted 2 October 2008; published online 30 January 2009 In order to resolve two previous conflicting reports on detectable but weak nuclear magnetic resonance NMR S signals in unenriched EuS, a sample of S-enriched EuS was prepared and the NMR and its temperature dependence were measured in the range from 1.3 to 4.2 K. It was verified that the T=0 extrapolated NMR signal has a value of 12.73 MHz 39 kG , not 5.4 MHz, as one group had reported. The temperature dependence of the NMR was used to assess the applicability of two proposed spin-wave-region power-law schemes. The schemes attempted to systematize and explain the simple power-law behaviors measured by NMR and other techniques that have been reported or have been present in measured data, but not reported for more than five decades. The scheme proposed by Koebler et al. Physica B 364, 55 2005 contends that the low-temperature magnetization of EuS follows a simple T2 behavior all the way up to 0.75Tc. The S spin-echo measurements are consistent with a power law, but cast doubt on a T2 dependence. Possible reasons for discrepancies between various EuS NMR measurements are discussed in the paper as well as means of resolving such issues by future experiments. © 2009 American Institute of Physics. DOI: 10.1063/1.3055270