Dissertation/Thesis Abstract

Magnetic spin dynamics in iron phthalocyanine thin films
by Byrne, Matthew P., M.S., California State University, Long Beach, 2016, 70; 10167519
Abstract (Summary)

This thesis aims to build upon the previous work done on the magnetic relaxation of iron(II) phthalocyanine (FePc) thin films by exploring the dynamic aspects of coercive fields in order to determine whether FePc can be classified as a low-dimensional material known as a single chain magnet. In thin films, the chain length is controlled by deposition temperature and therefore systematic studies of the chain-length dependent properties can be made. Hysteresis loops of FePc thin-films with five different chain lengths ranging from approx. 30 nm to 300 nm were measured at a range of sweep speeds from 10.4 mT/s to 1.07 mT/s. Each measurement was repeated at 5 different temperatures in the interval from 2.5 K to 3.8 K, where hysteresis was observed. Significant reductions in coercivity with slower sweep speeds reveal the non-equilibrium behavior of the magnetic states. Mean-field theory based on one-dimensional chains within a Glauber-Ising model suggests a power law behavior of coercivity with sweep rate. Indeed all experimental data is consistent with that behavior. The critical exponent varies from 0.521 to 0.153 for short to long chains. Given the limited observational window, coercivity due to inter-chain coupling cannot fully be ruled out, yet a large dynamic response in the coercivity supports the notion of a single chain magnet.

Indexing (document details)
Advisor: Gredig, Thomas
Commitee: Bill, Andreas, Gu, Jiyeong
School: California State University, Long Beach
Department: Physics and Astronomy
School Location: United States -- California
Source: MAI 56/02M(E), Masters Abstracts International
Subjects: Condensed matter physics
Keywords: Coercivity, Glauber, Ising model, Low dimensional, Phthalocyanine, Single chain magnets
Publication Number: 10167519
ISBN: 9781369218688
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