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【期刊论文】Influence of cohesive energy on unit cell volume of perovskite manganites La1-xMxMnO3
侯登录, G. D. Tang, D. L. Hou, Z. Z. Li, X. Zhao, W. H. Qi, S. P. Liu, F. W. Zhao
APPLIED PHYSICS LETTERS 89, 261919 (2006),-0001,():
-1年11月30日
Ionic size is considered to be an important factor influencing the unit cell volume of manganites with an ABO3 structure. For La1-xSrxMnO3, however, although the average effective ion radius of all cations taken together increases with increasing x, the unit cell volume decreases for x<0.5. In the case of La1-xNaxMnO3, the unit cell volume reaches a minimum when x = 0.3. Up to now, no satisfactory explanation of these phenomena has been found. In this letter, an explanation based on the ionic cohesive energy with a small additional metallic cohesive energy is described.
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【期刊论文】Studies on magnetic aftereffect of Fe3O4 nano-particles
侯登录, Deng-lu Hou, Zi-xia Du, Cai-xia Yue, Qing-hua Liu
Journal of Alloys and Compounds 429 (2007) 40-45,-0001,():
-1年11月30日
The magnetic aftereffects of Fe3O4 nano-particles were simulated by Preisach hysteresis model, the results showed excellent agreement with the experiment data. The simulating results showed that due to the wide distribution of interaction field, magnetization decay followed typical logarithmic time dependence, and the decay occurred more rapidly for field closer to the coercivity. The thermal fluctuation field and activation volume were also obtained, which are the main characteristics of the thermal fluctuations in magnetic recording medium. From the fact that activation volume is larger than the mean particle size, we deduced the reversal magnetization mechanism. One set of parameters used in simulating hysteresis loops and magnetic aftereffects has unified the hysteresis and magnetic aftereffect phenomena. The aftereffects under double-field were calculated, and the condition under which the time dependence of magnetization was non-monotonic was given.
Preisach model, Magnetic aftereffect, Fluctuation field, Activation volume
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【期刊论文】Preparation and Magnetic Properties of Fe0.7 Co0.3 - SiO2 Granular Alloy Solid
侯登录, D.L. Hou, G.D. Tang, W. Chen, Y. Liu, X.F. Nie, H.L. Luo
phys. Stat. sol. (a) 169, 131 (1998),-0001,():
-1年11月30日
The Fe0.7 Co0.3 - SiO2 granular alloy solid has been prepared using a sol-gel method, and investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The effective magnetic anisotropy KE has been measured by the law of approach to saturation (LATS). The evolution of the magnetic properties for the granular alloy solid during reducing is described and explained by means of particle size distribution and superparamagnetic behaviour. When the measuring temperature changes from 100 to 800 K, the variations of saturation magnetization, effective magnetic anisotropy and coercivity of the Fe0.7 Co0.3-SiO2 granular solid are much smaller than those of existing magnetic recording media. The Fe0.7 Co0.3 - SiO2 granular alloy solid has a potential for application in high density magnetic recording media, which can be used in a wide temperature range.
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【期刊论文】A Preisach characterization of the Barkhausen spectrum of a canonical ferromagnet SrRuO3
侯登录, R.M. Roshko, D.L. Huo
Physica B 306 (2001) 246-250,-0001,():
-1年11月30日
The irreversible response of a ferromagnetic pervoskite SrRuO3 with a Curie temperature TC = 160 K has been characterized experimentally by measuring the temperature dependence of the field cooled and zero field cooled moments over the temperature interval 5 K≤T≤180 K; in a sequence of applied fields up to the coercive field, and also the major hysteresis loop over the field range ∣ha∣≤40 kOe at a sequence of temperatures which span the ordered phase. The data have been analysed within the framework of a generalized version of the Preisach model of hysteresis which combines thermal fluctuations with the growth of the free energy barriers below TC. The numerical simulations replicate all of the principal structural systematics of the data, and yield details of the spectrum of Barkhausen instabilities in this material.
Preisach model, Ferromagnet, Irreversibility, Curie temperature
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【期刊论文】Magnetocaloric effect in La0.8-x Ndx Na0.2MnO3
侯登录, Deng-Lu Hou, Cai-Xia Yue, Yun Bai, Qing-Hua Liu, Xiu-Ying Zhao, Gui-De Tang
Solid State Communications 140 (2006) 459-463,-0001,():
-1年11月30日
Single-phase polycrystalline samples of La0.8-x Ndx Na0.2 MnO3 (x = 0.00, 0.05, 0.10, 0.15 and 0.20) were prepared by the sol–gel method. Investigations of Curie temperature and magnetic entropy change were carried out in the temperature range 240–340 K and magnetic field range 0–1 T. It was found that the Curie temperature TC decreases with increasing x, and that the maximum magnetic entropy change △S M , for x = 0.20, is 0.3692 J/mol K near the temperature 295 K. The results suggested that these perovskite manganites have some appropriate properties for a good candidate as magnetic refrigeration in the room temperature range.
A., Magnetically ordered materials, B., Chemical synthesis, D., Magnetocaloric effect, E., Magnetic measurements
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