Development of magnetoresistance sensing materials consisting of granulan materials with micro-patterned soft magnetic alloy films

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Currently, magnetic sensors have been important devices, and are actually used for many systems and purposes. Magnetic granular thin film is one of most important materials applicable to magnetic sensors because it can be made easily by a conventional sputtering technique. Furthermore, excellent field-sensitivity has been achieved in granular-in-gap (GIG) structures in which magnetic granular film is put in a lateral gap between a couple of soft magnetic alloy electrodes.In this study, we have investigated on (i) optimization of GIG structures, (ii) development of new structures for high field-sensitivity, (iii) development of new magnetic granular materials with large magnetoresistance, (iv) mechanism of the high field-sensitivity in GIG structures,(v) related magnetoresistance effects in GIG structures and (vi) development of actual GIG devices. By optimizing GIG structures, the magnitude and field-sensitivity of tunnel magnetoresistance are improved. This result is useful for preparing actual GIG devices. Concerning new materials, the largest room-temperature magnetoresistance has been found in CoFe-fluoride granular films, indicating that fluoride is a good barrier material for tunnel magnetoresistance. As a related magnetoresistance effect, enhanced magnetoresistance due to spin dependent single electron tunneling is observed at low temperatures in nanometer-sized GIG structures. Additionally, optimization of the electrical circuit for GIG sensors has been performed.