Size dependence of magnetization switching and its dispersion of Co/Pt nanodots under the assistance of radio frequency fields

Abstract

We have studied the dot size dependence of microwave assisted magnetization switching (MAS) on perpendicular magnetic Co/Pt multilayer dot array. The significant microwave assistance effect has been observed over the entire dot size D ranging from 50 nm to 330 nm examined in the present study. The MAS behavior, however, critically depends on D. The excitation frequency dependence of the switching field is well consistent with the spin wave theory, indicating that the magnetization precession in MAS is in accordance with the well defined eigenmodes depending on the dot diameter. The lowest order spin wave is only excited for D 100 nm, and then the MAS effect is well consistent with that of the single macrospin prediction. On the other hand, higher order spin waves are excited for D > 100 nm, giving rise to the significant enhancement of the MAS effect. The dispersion of MAS effect also depends on D and is significantly reduced for the region of D > 100 nm. This significant reduction of the dispersion is attributed to the essential feature of the MAS effect which is insensitive to the local fluctuation of anisotropy field, such as defect, damaged layer, and so on. V C 2014 AIP Publishing LLC. [http://dx.

Anomalous Hall Effect Measurement on Nanostructure with Magnetic Pulse Fields

“…In this section we brie y review the AHE measurement as a magnetic characterization method for nanostructures [10][11][12][13][14][15][16][17][18][19] . The AHE produces voltage difference in magnetic materials transverse to an applied current and a magnetization perpendicular to the current, as similar to the normal Hall effect by external magnetic eld in non-magnetic materials.…”

“…This fact indicates that AHE measurement keeps its quantitativeness in case of measurement on arrayed structures, allowing investigation of distribution and interactions. 17,19) …”

“…5) . Electrical detection of spin dependent transport properties has been also applied for various structures [8][9][10][11][12][13][14][15][16][17][18][19] . In particular, giant magnetoresistance (GMR) and tunnel magnetoresistance (TMR) in junction structures 8,9) have been intensively studied since in the structures magnetization can be manipulated by spin-polarized current.…”

“…In this paper, we overview anomalous Hall effect (AHE) measurement as a single nanoscale magnet measurement method [11][12][13][14][15][16][17][18][19] in the rst section. In the latter part of the article we introduce the result of magnetization switching experiments on nanosized Co/Pt multilayer dot in dynamic eld [13][14][15][16][17] .…”

“…The anomalous Hall effect is another spin dependent transport measurement and has been used as a probe to detect magnetization behavior of perpendicularly magnetized lm because of its terminal geometry. [10][11][12][13][14][15][16][17][18][19] Anomalous Hall effect measurement requires no reference layer and allows simple device structure compared with GMR/TMR junction structures. Operation frequency in GHz range is another requirements for recent magnetic and spintronic devices.…”