Zusammenfassung
The switching of electroplated Nickel- pillars with diameters smaller 170 nm and heights greater 300 nm was investigated. The nanomagnets were placed on top of the sensor either individually or in groups of 5 up to 13 in different patterns. The individual pillars show two types of hysteresis loops: one type resembles a perfect rectangular hysteresis trace over a wide temperature range, ...
Zusammenfassung
The switching of electroplated Nickel- pillars with diameters smaller 170 nm and heights greater 300 nm was investigated. The nanomagnets were placed on top of the sensor either individually or in groups of 5 up to 13 in different patterns. The individual pillars show two types of hysteresis loops: one type resembles a perfect rectangular hysteresis trace over a wide temperature range, the other type shows two steps in the Hall-voltage when magnetization direction is reversed. The switching field Hsw of a pillar with rectangular hysteresis trace was measured between 1.6 K and 225 K. Hsw decreases linearly with increasing temperature. Both results as well as the variation of switching fields of different �single domain� particles suggest, that oxide layers on the surface of the pillars strongly influence the magnetization reversal. Despite this complication small arrays of Ni pillars placed on the sensor display a well defined switching behavior. Different steps in the Hall-voltage reflect the switching of the individual magnets