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

目前，磁传感器已成为重要的设备，并实际用于许多系统和目的。磁性颗粒薄膜是一种适用于磁性传感器的重要材料之一，因为它可以用传统的溅射技术制备。此外，在间隙颗粒（GIG）结构中，磁性颗粒膜放置在一对软磁合金电极之间的横向间隙中，获得了优异的场灵敏度。在本研究中，我们研究了(i) GIG结构的优化，（ii）高场灵敏度新结构的开发，（iii）具有大磁阻的新型磁性颗粒材料的开发，（iv） GIG结构中高场灵敏度的机理，(v) GIG结构中相关的磁阻效应，以及（vi）实际GIG器件的开发。通过对GIG结构的优化，提高了隧道磁电阻的大小和场灵敏度。这个结果对于准备实际的GIG设备很有用。在新材料中，氟化咖啡颗粒膜的室温磁阻最大，表明氟是一种良好的隧道磁阻阻隔材料。作为相关的磁电阻效应，在纳米级GIG结构中，由于自旋相关的单电子隧道效应，在低温下观察到磁电阻增强。此外，还对GIG传感器的电路进行了优化。

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.