SPIN WAVES AND PHASE TRANSITIONS IN FERROMAGNETIC SUPERLATTICES
type: CreativeWork
description: With the advance in experimental techniques such as sputtering and epitaxy, spin excitations in magnetic superlattices have been the subject of increasing interest in recent years. Much of this work is motivated by a desire to achieve technically useful characteristics, such as man-tailored superlattice materials, surface and interface condition probe etc. In this dissertation, the spin waves in both magnetostatic region and exchange region, as well as phase transitions in Ising Model for ferromagnetic superlattices are studied. A new method of recurrence relations is used for the first time to study the spin waves or Curie temperatures in ferromagnetic superlattices. Compared with the previous method, such as transfer matrix method, this recurrence relation method has its unique advantages. Using this method, we can relate the potentials or spin constants of any two layers for a periodic superlattice in an analytical expression, and extend our results to an infinite limit easily. In the magnetostatic region, a macroscopic approach based on Maxwell's equations is used and the following superlattice structures are studied: I. Ferromagnetic / Nonmagnetic Superlattices With a Modified Surface or Inner Layer: It is found that for superlattices with modified magnetization MI at the surface layer, in addition to the spin waves present originally, there is a new surface superlattice spin wave if the wave vector is greater than a critical kc for a given M1. However, for defect superlattices, the localized mode always exists for M1 ? M. 2. Ferromagnetic / Nonmagnetic Superlattices With Different Layer Magnetization or Thickness: It is found that in an N layer superlattice with uniformly increased magnetization from left to right, for sufficient large k, there are N localized modes at the N left interfaces of the N layers (for positive q). 3. Three Models of Ferromagnetic / Ferromagnetic Superlattices: In the two-component superlattices, two surface modes are found to be char…
abstract: With the advance in experimental techniques such as sputtering and epitaxy, spin excitations in magnetic superlattices have been the subject of increasing interest in recent years. Much of this work is motivated by a desire to achieve technically useful characteristics, such as man-tailored superlattice materials, surface and interface condition probe etc. In this dissertation, the spin waves in both magnetostatic region and exchange region, as well as phase transitions in Ising Model for ferromagnetic superlattices are studied. A new method of recurrence relations is used for the first time to study the spin waves or Curie temperatures in ferromagnetic superlattices. Compared with the previous method, such as transfer matrix method, this recurrence relation method has its unique advantages. Using this method, we can relate the potentials or spin constants of any two layers for a periodic superlattice in an analytical expression, and extend our results to an infinite limit easily. In the magnetostatic region, a macroscopic approach based on Maxwell's equations is used and the following superlattice structures are studied: I. Ferromagnetic / Nonmagnetic Superlattices With a Modified Surface or Inner Layer: It is found that for superlattices with modified magnetization MI at the surface layer, in addition to the spin waves present originally, there is a new surface superlattice spin wave if the wave vector is greater than a critical kc for a given M1. However, for defect superlattices, the localized mode always exists for M1 ? M. 2. Ferromagnetic / Nonmagnetic Superlattices With Different Layer Magnetization or Thickness: It is found that in an N layer superlattice with uniformly increased magnetization from left to right, for sufficient large k, there are N localized modes at the N left interfaces of the N layers (for positive q). 3. Three Models of Ferromagnetic / Ferromagnetic Superlattices: In the two-component superlattices, two surface modes are found to be char…
author: CHEN FENG
keywords: Superlattice, Spin Wave, Curie Temperature, Magnetostatic Region, Exchange Region, Recurrence Relations
date published: 1997
date modified: 2026-07-24T03:32:43Z
provider: National University of Singapore
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: National University of Singapore