Acquisition of vector hysteresis loops from micro-arrays of nano-magnets

A modified scanning Kerr microscope has been used as a static Kerr magnetometer to acquire in-plane vector hysteresis loops from square Si/Ta(50 angstrom)/Co(80)Fe(20)(40 angstrom)/Ni(88)Fe(12)(108 angstrom)/Ta(100 angstrom) elements with size ranging from 123 nm to 10 mu m. The nanoscale elements were arranged in square arrays of 4 mu m size. The laser beam was focused to a sub-micron spot, while polarization changes were recorded with an optical bridge detector containing a beam-splitting polarizer and two quadrant photodiodes. The coercive field exhibited a non-monotonic increase from 11 Oe in the 10 mu m element to 170 Oe in the 123 nm elements. Loops acquired with the field applied parallel to the easy and hard in-plane uniaxial anisotropy axes were observed to become more similar in shape as the element size decreased. (C) 2006 Elsevier B.V. All rights reserved.