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Ultrafast spin dynamics in half-meta...

Zhang, Qiang.

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Ultrafast spin dynamics in half-metallic ferromagnetic thin film.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Ultrafast spin dynamics in half-metallic ferromagnetic thin film./
作者:	Zhang, Qiang.
面頁冊數:	177 p.
附註:	Source: Dissertation Abstracts International, Volume: 66-05, Section: B, page: 2646.
Contained By:	Dissertation Abstracts International66-05B.
標題:	Physics, Condensed Matter. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3174709
ISBN:	0542129159

Ultrafast spin dynamics in half-metallic ferromagnetic thin film.
Zhang, Qiang.

Ultrafast spin dynamics in half-metallic ferromagnetic thin film. - 177 p.

Source: Dissertation Abstracts International, Volume: 66-05, Section: B, page: 2646.

Thesis (Ph.D.)--Brown University, 2005.

Manipulation of electron spins by optical means is anticipated to play a key role in future high-density magnetic storage technology. The ability to maneuver spins beyond thermal excitation regime is of great interests because of its potential in breaking the "bottle neck" in current magnetic recording speed. Scientifically, initial studies of spin dynamics in ferromagnetic materials by ultrafast laser pulses have revealed many intriguing phenomena, but such studies have been mostly limited to conventional transition metals and many novel materials still remain unexplored. CrO2 has provided us such a good model system. The availability of high-quality single-crystal CrO2 film has stimulated extensive studies of the properties of this material in the last few years and revealed that it is a ferromagnetic half metal, namely, the spins are highly polarized in vicinity of the Fermi surface. The transient spin dynamics study has given us an opportunity to look at CrO2 from another aspect, which has never be seen before.

ISBN: 0542129159Subjects--Topical Terms:

1018743
Physics, Condensed Matter.

Ultrafast spin dynamics in half-metallic ferromagnetic thin film.
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245 1 0 $a Ultrafast spin dynamics in half-metallic ferromagnetic thin film.
300 $a 177 p.
500 $a Source: Dissertation Abstracts International, Volume: 66-05, Section: B, page: 2646.
500 $a Adviser: Arto V. Nurmikko.
502 $a Thesis (Ph.D.)--Brown University, 2005.
520 $a Manipulation of electron spins by optical means is anticipated to play a key role in future high-density magnetic storage technology. The ability to maneuver spins beyond thermal excitation regime is of great interests because of its potential in breaking the "bottle neck" in current magnetic recording speed. Scientifically, initial studies of spin dynamics in ferromagnetic materials by ultrafast laser pulses have revealed many intriguing phenomena, but such studies have been mostly limited to conventional transition metals and many novel materials still remain unexplored. CrO2 has provided us such a good model system. The availability of high-quality single-crystal CrO2 film has stimulated extensive studies of the properties of this material in the last few years and revealed that it is a ferromagnetic half metal, namely, the spins are highly polarized in vicinity of the Fermi surface. The transient spin dynamics study has given us an opportunity to look at CrO2 from another aspect, which has never be seen before.
520 $a In this thesis, transient magneto-optic Kerr measurement utilizing ultrafast laser pulse excitation and detection has been performed to study the spin dynamics in epitaxial CrO2 films. Different microscopic contributions leading to incoherent spin thermalization and relaxation on distinct time scales have been identified in a modified three-temperature model by taking into account the nonthermal electrons, which has been mostly neglected in previous studies. Interestingly, the spins and thermalized electrons seemed to have been decoupled in these measurements, which could be attributed to the half-metallic nature of the material.
520 $a Coherent magnetization precession directly triggered by photoexcitation was also found to be present in CrO2, when an external magnetic field of proper strength was applied to the magnetic hard axis of the film. Furthermore, coherent phase control of these oscillations could be achieved by employing two temporally separated excitation pulses. The above findings can be very well described by a simple model based on Landau-Lifshitz-Gilbert (LLG) equation. In this model, the driving force of the coherent magnetization rotation was provided by the optically modulated magnetocrystalline anisotropy. Direct experimental evidence of the magnetic anisotropy relaxation was provided.
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791 $a Ph.D.
792 $a 2005
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