This Small Business Innovation Research Phase I project will investigate the feasibility of a new magnetic imaging method with nano-scale spatial resolution and high sensitivity. The new method will combine the emerging technology of the magnetic tunnel junction (MTJ) sensor -- a device which provides a factor of ten improvement in magnetoresistance ratio versus the best competing giant magnetoresistive devices -- with the workhorse technique of atomic force microscopy (AFM). MTJ sensors with magnetoresistance ratios on the order of 100-200% will be fabricated and integrated into the standard cantilever-based methodology of AFM tips. High spatial resolution will be obtained by patterning MTJ sensors to 100 nanometer-dimensions and by using AFM's standard force-feedback methods to ensure minimal standoff between the sensor and the sample. The new method will be quantitative and non-invasive, will require no special sample preparation, and will have a magnetic sensitivity which is 100 times better than magnetic force microscopy, the current workhorse technique for imaging magnetic fields at the nanoscale. The new technique will also be able to measure magnetic fields created by current flow, a capability which is difficult or impossible with most competing techniques.
The research will have a variety of scientific, economic, and social impacts. The new nanoprobe will immediately present compelling advantages to any engineer or technician who relies on scanning probe techniques to measure magnetic or current-carrying materials. It would therefore be an enabling capability for the semiconductor and disk drive industries, where the new nanoprobe could be used to image disk media and recording heads, and to visualize and quantify current flow in both new prototypes and faulty devices. Similarly, engineers working on the next generation of magnetic random access memories will be able to quantitatively measure new devices with high accuracy. Taking a longer view, progress in the fields as critical and disparate as nanotechnology, neuroscience, and bio-engineering depends on the availability of tools which can non-destructively measure physical properties of materials and devices at small length scales. For example, researchers wishing to directly measure electrical activity in the brain will be able to use the MTJ nanoprobe to obtain a combination of spatial resolution and sensitivity far superior to anything else currently available. Finally, the development of new tools for visualization of physical phenomena is always critical for creating scientific awareness and understanding in the larger community.
