Accession Number : ADA308548

Title :   Physical Properties of Nanometer-Scale Magnets.

Descriptive Note : Final rept. 15 Jan 93-14 Jan 96,

Corporate Author : CALIFORNIA UNIV SANTA BARBARA DEPT OF PHYSICS

Personal Author(s) : Awschalom, David D.

PDF Url : ADA308548

Report Date : 14 JAN 1996

Pagination or Media Count : 10

Abstract : As described in our original proposal, we have spent the final year of our research program investigating the physical properties of nanometer-scale magnets. This has involved several projects and associated experimental techniques. Arrays of nanometer-scale iron particles are grown by local organometallic deposition with a scanning tunneling microscope. The average magnetic properties are studied at low temperatures (5 - 100 K) with a two-dimensional hole gas Hall magnetometer. Rotation of the net array magnetization occurs by both reversible and irreversible modes, the latter revealed by Barkhausen jumps. Direct spatially-resolved measurements at room temperature with a magnetic force microscope show that the discrete jumps are due to the sudden switching of individual single-domain particles. Particles that appear structurally similar are found to be magnetically distinct. The present work employs the additive technique of local organometallic deposition with a scanning tunneling microscope (STM) to produce nanometer-scale iron particles with control of the shape and orientation. The average magnetic properties of an array of particles is compared with the properties of individual particles by complementary low temperature Hall magnetometer and room temperature magnetic force microscope (MFM) measurements, the latter producing some of the highest resolution magnetic images of submicron structures to date. Although the particles formed with the STM are seen to be structurally similar through atomic-scale topographic studies, they vary magnetically in terms of coercive fields, suggesting that anisotropy on a length scale smaller than the spatial resolution of our probes (-25 nm) is playing an important role.

Descriptors :   *MAGNETIC FIELDS, *MAGNETS, SCANNING ELECTRON MICROSCOPES, PHYSICAL PROPERTIES, HALL EFFECT, TUNNELING(ELECTRONICS), ORGANOMETALLIC COMPOUNDS, SEMICONDUCTORS, ELECTRON SPIN RESONANCE, MAGNETIZATION, MAGNETOMETERS, IRON ORGANIC COMPOUNDS.

Subject Categories : Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE