Imaging and magnetometry of switching in nanometer-scale iron particles

The reversal mechanisms in arrays of nanometer-scale (<40 nn diameter) iron particles are studied by low-temperature Hall magnetometry and room-temperature magnetic force microscopy, Rotation of the net array magnetization at low temperatures (20 K) occurs by both reversible and irreversible modes, the latter revealed by Barkhausen jumps. Spatially resolved measurements at room temperature show the particles to be single domain with remanence and coercivity indicating they are not superparamagnetic. Individual particles are observed to switch irreversibly over a small field ranee (<10 Oe) between preferred magnetic directions parallel to the growth direction of the particles. Scaling of the arrays offers the possibility of magnetic storage at the 45 Gbit/in.(2) level, nearly 50 times greater than current technology. (C) 1996 American Institute of Physics.