The Magnetic Materials thrust comprises several areas:

• High resolution magnetic imaging
  Establishing the microstructural details of the magnetic field distributions produced by such systems through ultra-high resolution and field sensitivity imaging is crucial to the elucidation of the basic physical phenomena that govern the behaviors of those systems. The development of magnetic force microscopy (MFM) has greatly contributed to this endeavor but MFM has notable limitations. It measures the field gradient as opposed to the field itself. This complicates analysis and reduces the accuracy of the field distribution determination. In addition, the self-field of the MFM tip can be quite large, of order 1000 Gauss or more, giving rise to an invasive probe process in which the magnetic properties of the system under investigation can be perturbed by the investigative tool.

  To overcome the deficiencies in MFM we have developed a method to estimate the complete magnetization in thin-film longitudinal recording media from MFM data. The method uses a medium model described by a Voronoi tessellation of the film plane. We have also developed a method of ultra-high resolution magnetic imaging in situ to a magnetic recording drive. Enhanced magnetization images are produced through deconvolution of the linearized readback by a synthesized two-dimensional head response kernel. While the current sub-25 nm resolution of this technique is on the same order as MFM, there are numerous advantages: this is a nondestructive tool, it is performed in situ to a commercial HDD, has ultra-high resolution, high SNR, and this technique can be performed easily (at the manufacturing or development site) without any elaborate tools. We are applying this technique to recording investigations and are exploring failure analysis.

  We are finishing the development of a hybrid system, one that combines the high spatial resolution raster-scanned stage with sub-nanometer resolution and the convenience of a high-resolution room temperature Giant Magnetoresistive sensor. Through sophisticated signal techniques developed for the in situ drive imaging, we will deconvolve the spreading function from the sensor to deliver superior resolution magnetic images.

  The discovery of Extraordinary Magnetoresistance (EMR) by Solin and coworkers and the fabrication of nanoscopic EMR field sensors [recently chosen by the American Physical Society as one of the most important achievements of 2002] now provide the opportunity to advance the state of the art of semiconductor based scanning magnetic field probes by offering at least an order of magnitude higher sensitivity and an order of magnitude higher spatial resolution over a temperature range from liquid He temperatures to room temperature without sacrificing any of the intrinsic advantages of the Scanning Hall Probe Microscopy.

• Magnetic phase transitions
  One of the most active current areas of interest in fundamental condensed matter science is the study of magnetic phase transitions (MPT). This interest is the result of the embodiment in MPT phenomena of the forefront theoretical challenges posed by frustration, spin dynamics, and domain wall structure and dynamics in magnetic materials as well as vortex structure and dynamics in superconductors. Armed with a diverse expertise and a broad set of experimental tools, some of which are unique, we are in an excellent position to advance the fundamental understanding of MPT. Accordingly, we are embarking on an integrated research program which probes several key questions in this field by bringing to bear currently available instrumentation and expertise and by incorporating the new scanning extraordinary magnetoresistance probe microscope (SEMRPM) which is currently under development. The envisioned research program includes: (1) testing resonance valence bond theory in real systems, (2) studying vortex phases in high-temperature superconductors, and (3) characterizing magnetic ordering transitions in molecule-based magnetic materials.
• Superior magnetic sensors
  
• Advanced magnetic storage media