Sensitive detection of irreversible switching in a single FePt nanosized dot

Abstract

Magnetization of an isolated single dot as small as 60 nm in diameter fabricated from a single crystal L10-FePt(001) film has been measured by detection of the anomalous Hall effect in the temperature range from 10 to 300 K. Over the whole temperature range, the dots with diameter ranging from 60 nm to 12 μm exhibit perfect rectangular magnetization loops with coercivity almost constant regardless of the very large difference in diameter. The activation energy has been evaluated to be about 4×10−19 J, equivalent to the domain-wall energy times the square of the domain-wall thickness, suggesting that the magnetization reversals are initiated by nucleation of reversed embryo with the dimension of the exchange length.

Anomalous Hall Effect Measurement on Nanostructure with Magnetic Pulse Fields

“…1. 10,12) This structure has similarity with the Hall cross of Co-Cr columnar lm mentioned above, except that the surrounding excess magnetic materials is replaced by nonmagnetic material. In such structure, the AHE signal intensity is expected to be signi cantly smaller compared to continuous lm and depends on the sample geometry.…”

“…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.…”

“…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.…”

“…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.…”

“…Understanding of magnetization behavior of magnetic nanostructures has become more important since behavior of those nanostructures dominate device properties. In order to study magnetization behavior of magnetic nanostructures, various measurement techniques had been developed for nanostructures [1][2][3][4][5][6][7][8][9][10] because the low sensitivity of conventional magnetometry is insuf cient to detect magnetization reversal of a single structures. Detection of magnetic ux would be the most straightforward method.…”