Zero Field Nmr Study on a Spin Glass: Iron-Doped 2hydrogen-Niobium Diselenide

We have used spin echoes to study the ('93)Nb NQR in 2H-NbSe(,2)Fe(,x). We measured (intensity) x (temperature), and T(,1P) (spin-lattice relaxation parameter) and T(,2) (spin-spin relaxation time) as a function of temperature. Our data reveal dramatic difference between non-spin glass samples (x = 0, 0.25%, 1% and 5%) and spin glass samples (x = 8%, 10% and 12%). Defining the spin glass transition temperature T(,g) by the cusp of the susceptibility versus temperature curve, we find well-defined minima at T = T(,g) in (intensity) x (temperature), T(,1P) and T(,2) as a function of temperature. Deduction of a correlation time of Fe spins from T(,1P) and T(,2) is complicated by the intensity changes which imply that one observes different groups of nuclei at different temperatures. We propose a two-correlation-time model, which utilizes the anisotropy of the exchange interaction, to overcome this difficulty. All of our NQR results and the model calculation of the correlation times of Fe spins are best described by the phase transition picture of spin glasses.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Chen, Men-Chee

• Physics, Nuclear

Language dc:language

eng

Identifier

(UMI)AAI8218443

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/77345