Magnetic force microscope tip-induced remagnetization of CoPt nanodisks with perpendicular anisotropy

Abstract

We report on the results of a magnetic force microscopy investigation of remagnetization processes in arrays of CoPt nanodisks with diameters of 35 and 200 nm and a thickness of 9.8 nm fabricated by e-beam lithography and ion etching. The controllable magnetization reversal of individual CoPt nanodisks by the magnetic force microscope ͑MFM͒ tip-induced magnetic field was demonstrated. We observed experimentally two essentially different processes of tip-induced remagnetization. Magnetization reversal of 200 nm disks was observed when the probe moved across the particle while in case of 35 nm nanodisks one-touch remagnetization was realized. Micromagnetic modeling based on the Landau-Lifshitz-Gilbert ͑LLG͒ equation demonstrated that the tip-induced magnetization reversal occurs through the essentially inhomogeneous states. Computer simulations confirmed that in case of 200 nm disks the mechanism of embryo nucleation with reversed magnetization and further dynamic propagation following the probe moving across the particle was realized. On the other hand one-touch remagnetization of 35 nm disks occurs through the inhomogeneous vortexlike state. Micromagnetic LLG simulations showed that magnetization reversal in an inhomogeneous MFM probe field has a lower energy barrier in comparison with the mechanism of coherent rotation, which takes place in a homogeneous external magnetic field.

Shape and strain-induced magnetization reorientation and magnetic anisotropy in thin film Ti/CoCrPt/Ti lines and rings

“…The experiment does not give values of anisotropy directly, but instead measures the remanent magnetization direction, as deduced from the stray-field distribution. The magnetization of the tip influences the magnetic state 104 and may enhance the apparent out-of-plane magnetization component. The model is itself limited by the neglect of the surface magnetoelastic anisotropy term ͑B CoCrPt-O SU ͒, which would favor magnetization along the line length, and by neglect of terms of minor magnitude such as the second-order magnetoelastic surface and bulk magnetocrystalline anisotropy terms.…”

Локализованные Моды Спин-Волнового Резонанса Ферромагнитных Микрополосок В Поле Магнитного Зонда

“…4, c, d). Поле зонда вначале вызывает небольшие возмущения намаг-ниченности микрополоски, а при малом расстоянии между зондом и образцом приводит к эффектам пе-ремагничивания [16]. Для рассматриваемых параметров системы критическое расстояние составляло 40 nm.…”

Tutorial Section on Nanomagnetism

“…5 It is also possible to derive an expression for t 0 , which according to the model by Brown 6 is given by This has been measured to be 10 ns in 2-nm diameter Fe nanoparticles embedded in Ag matrices 4 and 1 ns in 35-nm diameter  10-nm thickness CoPt discs.…”