Premium
Nanoparticle morphology in FeCo–Al 2 O 3 granular films with tunneling giant magnetoresistance
Author(s) -
Wang Changzheng,
Zhang Yiqing,
Xiao Xiaoguang,
Hu Haiquan,
Rong Yonghua
Publication year - 2006
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200521268
Subject(s) - materials science , high resolution transmission electron microscopy , volume fraction , amorphous solid , nanoparticle , giant magnetoresistance , grain size , magnetoresistance , condensed matter physics , quantum tunnelling , sputter deposition , morphology (biology) , nanotechnology , thin film , transmission electron microscopy , sputtering , composite material , crystallography , chemistry , physics , magnetic field , optoelectronics , quantum mechanics , biology , genetics
A series of FeCo–Al 2 O 3 granular films were prepared by a magnetron‐controlled sputtering system. The tunneling giant magnetoresistance and nanoparticle morphology of FeCo particles in FeCo–Al 2 O 3 granular films were directly determined utilizing a conventional four‐probe method and TEM (HRTEM) observation, respectively. The results indicated that the tunneling giant magnetoresistance can reach a maximum of 6.9% at about 32.8 vol% FeCo particles, so far the highest value reported at room temperature and under an applied field of 12.5 kOe. Meanwhile, the sensitivity of TMR also reaches a maximum at about 32.8 vol% FeCo particles. In addition, TEM and HRTEM observation disclosed that FeCo–Al 2 O 3 films consist of FeCo nanoparticles with bcc structure or amorphous FeCo phase dispersed in amorphous or crystalline Al 2 O 3 matrix. For films with lower volume fraction of FeCo particles, the size distribution of FeCo particles satisfied a log‐normal function. With increasing volume fraction of FeCo particles, the size distribution of FeCo particles deviated gradually from a log‐normal function. Meanwhile, the average size of FeCo particles increased monotonically with increasing volume fraction of FeCo particles, leading to the fact that TMR can reach a peak value at a certain middle particle size. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)