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

Chen, Men-Chee

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https://hdl.handle.net/2142/77345 Copy

Description

Title

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

Author(s)

Chen, Men-Chee

Issue Date

1982

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Physics, Nuclear

Language

eng

Abstract

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.

Graduation Semester

1982

Type of Resource

text

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http://hdl.handle.net/2142/77345

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