Multilayer Giant Magnetoresistive Thin Films

Professor Jian-Gang Zhu of the Department of Electrical Engineering is doing research which utilizes a numerical micromagnetic model implemented on supercomputers to investigate the magnetic hysteresis and fundamental magnetization processes in multilayer giant magnetoresistive (GMR) films. This work is aimed at the development of new technologies for improved disk-drive recording for the storage and retrieval of information.

Giant magnetoresistive thin films are the key to a revolutionary change in this area. These materials are used in the manufacture of magnetoresistive sensors which, because of their ultrasensitivity, would replace the inductive sensors now in use for data storage and retrieval in most computer data storage systems.

The fundamental difference between the magnetoresistive sensor and inductive sensor is that the former directly senses the flux from opposing magnetic fields, while the latter uses an induction coil and transducer to sense variations in the magnetic flux. Because they are so ultrasensitive, magnetoresistive sensors are able to retrieve information far more efficiently and at higher data rates than ever before.

However, GMR films offer their own unique set of challenges. While the soft magnetic properties of the films allow them to perform as ultrasensitive flux sensors, these same properties also predispose these materials to domain instability, or various magnetic moments occuring at the same time. An important aspect of Dr. Zhu's research is understanding and controlling domain instability.

Professor Zhu's first study using supercomputers allowed him to develop models to correlate intrinsic materials properities to the recording process and to modify materials structures to improve storage density. His current work continues to expand our understanding by studying the underlying physics of the low field characteristics in GMR films.

Dr. Zhu has been a faculty member at the University of Minnesota for nearly 5 years and has an extensive research program. He has graduated 5 Ph.Ds and 6 masters students, all of whom are working in the U.S. magnetic recording industry. His research is funded in part by IBM, the Department of Commerce's Advanced Technology Program, the Office of Naval Research, and Seagate Technology, a Minneapolis based disk drive manufacturer. In 1993 he received the NSF Presidential Young Investigator Award. He currently holds a McKnight-Land Grant Professorship at the University of Minnesota.

Please see the following University of Minnesota Supercomputer Institute research reports for additional information. They are available by sending email to kilber@msi.umn.edu

• UMSI 94/51 February 1994
  Narrow Track Recording in Perpendicular Thin Film Media
  Jian-Gang Zhu and Xiao-Guang Ye

• UMSI 94/52 February 1994
  Advanced Microstructures of Thin Film Media for Ultra-High Area Recording Densities
  Jian-Gang Zhu and Xiao-Guang Ye

• UMSI 94/53 February 1994
  Micromagnetic Modeling and Experimental Study of Transition Noise Correlation in Thin Film Media
  Jian-Gang Zhu and Haiyun Wang