ESSENTIAL FACTORS INFLUENCING TUNNELING GIANT MAGNETORESISTANCE OF GRANULAR FILMS

2006 ◽  
Vol 20 (02n03) ◽  
pp. 129-140
Author(s):  
CHANGZHENG WANG ◽  
YONGHUA RONG ◽  
T. Y. HSU
Keyword(s):  
Size Distribution ◽  
Giant Magnetoresistance ◽  
Volume Fraction ◽  
Critical Size ◽  
Phenomenological Theory ◽  
Normal Function ◽  
Single Domain ◽  
Measured Temperature ◽  
Granular Films ◽  
Granule Matrix

A series of ferromagnetic-insulator granular films were prepared at room temperature with a spc350 multi-target magnetron controlled sputtering system and all of the tunneling giant magnetoresistences were measured with the conventional four probes method. Experimental results revealed that TMR depends strongly on the magnetic granule, matrix and the size distribution of magnetic granules. Accordingly, a modified phenomenological theory is presented to investigate comprehensively the effect of the magnetic granule, matrix and the size distribution of magnetic granules on the TMR. In this theory, the size distribution of granules was described by the log-normal function and all granules can be divided into three categories which have different contributions on TMR by two critical sizes: D1(T) as the critical size distinguishing superparamagnetic granules from single domain ferromagnetic granules and D2(T) as the critical size distinguishing the single domain from the multi-domain. The calculated results, including TMR versus applied magnetic field, measured temperature, granule size or volume fraction, are in agreement with the experiments when the single domain ferromagnetic granules play a key role in TMR for granular films, which indicates that our modified model is reasonable.

The effect of the size distribution on the giant magnetoresistance in magnetic granular films

2004 ◽  
Vol 241 (4) ◽  
pp. 916-924
Author(s):  
Changzheng Wang ◽  
Zhenghong Guo ◽  
Yonghua Rong ◽  
T. Y. Hsu
Keyword(s):  
Size Distribution ◽  
Giant Magnetoresistance ◽  
Granular Films

Materials science aspects in designing giant magnetoresistance in heterogeneous Cu1-xCox thin films

1993 ◽  
Vol 51 ◽  
pp. 1018-1019
Author(s):  
Andreas Hütten ◽  
Gareth Thomas
Keyword(s):  
Thin Films ◽  
Giant Magnetoresistance ◽  
Materials Science ◽  
Volume Fraction ◽  
Mean Free Path ◽  
Single Domain ◽  
New Materials ◽  
Multilayered Structures ◽  
The Mean ◽  
Theoretical Analyses

The recent discovery of giant magnetoresistance (GMR) in heterogeneous Cu1-xCox thin films has brought new insights in the phenomenon of GMR, which was previously believed to be restricted to multilayered structures only. Subsequent theoretical analyses of GMR in this new materials class have shown that GMR is mainly controlled by the mean radius and the volume fraction of single domain ferromagnetic particles. In addition to these parameters, the mean free path for electron in the non-magnetic matrix as well as coherency between particles and matrix are influencing the amplitude of GMR. Clearly, the key to increase the amplitude of GMR is to determine the decomposition kinetics and from which to optimize the single domain ferromagnetic Co particle size distribution in heterogeneous Cu1-xCox thin films.Cu81Col9 films, 50 nm in thickness, have been deposited by dc magnetron sputtering from separate Cu and Co targets onto 30 nm thick silicon nitride electron transparent grids.

A phenomenological theory of the granular size effect on the giant magnetoresistance of granular films

2004 ◽  
Vol 277 (3) ◽  
pp. 273-280 ◽  
Author(s):  
Changzheng Wang ◽  
Zhenghong Guo ◽  
Yonghua Rong ◽  
T.Y. Hsu (Xu Zuyao)
Keyword(s):  
Size Effect ◽  
Giant Magnetoresistance ◽  
Phenomenological Theory ◽  
Granular Films

scholarly journals Intercomparison between the aerosol optical properties retrieved by different inversion methods from SKYNET sky radiometer observations over Qionghai and Yucheng in China

2020 ◽  
Vol 13 (3) ◽  
pp. 1195-1212 ◽  
Author(s):  
Zhe Jiang ◽  
Minzheng Duan ◽  
Huizheng Che ◽  
Wenxing Zhang ◽  
Teruyuki Nakajima ◽  
...  
Keyword(s):  
Optical Properties ◽  
Size Distribution ◽  
Volume Fraction ◽  
Ground Surface ◽  
Correlation Coefficients ◽  
Single Scattering ◽  
Normal Function ◽  
Aerosol Optical Properties ◽  
Coarse Mode ◽  
Volume Size

Abstract. This study analyzed the aerosol optical properties derived by SKYRAD.pack versions 5.0 and 4.2 (referred to as V5.0 and V4.2) using the radiometer measurements over Qionghai and Yucheng in China, two new sites of the sky radiometer network (SKYNET). As V5.0 uses an a priori size distribution function (SDF) of a bimodal log-normal function, the volume size distribution retrieved by V5.0 presented bimodal patterns with a 0.1–0.2 µm fine particle mode and a 3.0–6.0 µm coarse particle mode both over Qionghai and Yucheng. The differences in the volume size distributions between the two versions were very large for the coarse mode with a radius of over 5 µm. The single scattering albedos (SSAs) by V5.0 correlated with SSAs by V4.2 with R=0.88, 0.87, 0.90, 0.88, and 0.92 at wavelengths of 400, 500, 670, 870, and 1020 nm over Qionghai, respectively. The correlation coefficients were around 0.95, 0.95, 0.96, 0.94, and 0.91 at the five channels in Yucheng. An error of ±5 % for the solid view angle (SVA) introduced about ±2 % differences in retrieved SSA values both by V4.2 and V5.0. An error of ±50 % for ground surface albedo (Ag) caused about 1 % averaged differences in retrieved SSA values by the two versions. With the atmospheric pressure (PRS) increased by 1 %, 2 %, 3 %, and 4 %, the averaged changes in SSAs did not exceed 0.8 % both by V4.2 and V5.0. The SSA differences at 500 nm between the two versions decreased, while aerosol optical depths (AODs) increased over both sites. The seasonal variability of the aerosol properties over Qionghai and Yucheng was investigated based on SKYRAD.pack V5.0. The seasonal averaged AOD over Qionghai had higher values in spring, winter, and autumn and lower values in summer. The AOD averages were commonly higher in summer and spring than in winter and autumn in Yucheng. The lowest seasonal averaged SSAs were both observed in winter at the two sites. The fraction of the fine aerosol particles was much smaller in summer than in other seasons over Qionghai; the volume fraction of the coarse-mode particle in Yucheng had much larger values compared to the fine-mode particle in all seasons. The validation results provide valuable references for continued improvement of the retrieval algorithms of SKYNET and other aerosol observational networks.

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