Manifestation of Nonconservation of Magnetization Modulus in Steady State Domain Wall Motion

• Main Authors: Chen, Shoan-Chung, 陳聖鐘
• Other Authors: Tzay-Ming Hong
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/45789063577445744998

博士 === 國立清華大學 === 物理學系 === 85 === The generalized Slonczewski equations have been applied to study the influenceof the field normal to the anisotropy axis on the Walker critical field, critical velocity and the maximum velocity of the steady-state domain wall motion. It is shown that the maximum value of the steady-state velocity of the domain wall is the Schlomann limiting velocity which is drive field dependent. The dependences of the Walker critical field and velocity as well as Schlomann limiting velocity on the field normal to the anisotropy axis have been obtained. The new equations take into account the relaxational dynamics of magnetization modulus first introduced into the Landau-Lifshitz equation by Bar'yakhtar. In the derivation of linear mobility, a new expression of a relaxation parameter is obtained. It reaveals a relation between ferromagnetic resonance(FMR) line width and the relaxation parameter obtained from mobility measurement. Based on this relation, it is found that the nonconservation of magnetization modulus gives rise to a larger contribution to the domain wall drag in ferromagnets with a narrower FMR line width than in ones with a wider line width. The description of the steady state domain wall motion in the traditional Landau-Lifshitz-Gilbert equation may give essentially the same dependency upon the drive field and transverse field provided if the phenomenological relaxation constant is deduced directly from experimental data on the domain wall mobility, instead of from a ferromagnet with a wide resonance line width. It is also found that the drag force due to nonconservation of magnetization modulus is enhanced by drive field but depressed by transeverse field.