共查询到18条相似文献,搜索用时 359 毫秒
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本文研究了Co_xZn-(1-x)(Pe_yCr(1-x)_2O_4尖晶石系统的磁性,测量了不同成份样品的低频弱场交流磁化率与低场直流磁化强度的温度关系。根据实验结果,给出了该系统可能的磁相图。发现在该系统中相当宽的成份范围内,都存在自旋玻璃的重入现象。同时发现,自旋玻璃的重入温度随磁性离子浓度增加而增加。这些行为是磁性离子浓度含量较高和多种磁性离子共存系统的共同特性。还讨论了自旋玻璃重入行为的机制。认为该尖晶石系统中的重入自旋玻璃态,是由亚铁磁长程序解体而形成的大量亚铁磁微畴或自旋团与自旋玻璃共存的状态。 相似文献
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用超导量子干涉器(SQUID)磁强计对稀释磁性半导体Zn1-xMnxSe(0.1≤x≤0.50)的低温低场直流磁化率作了测量,测量温度从4.2K到30K,测量磁场为15Oe。当x≥0.30时,从磁化率-温度曲线的浑圆峰值,观察到了自旋玻璃的转变。自旋玻璃的转变温度Tf,对x=0.30,0.40,0.50,分别为10.5K,16K,19.5K。给出了顺磁相和自旋玻璃相的相图。比较了Zn1-xMnxSe和Cd1-xMnxSe的自旋玻璃转变温度,发现对同样的Mn离子浓度,Zn1-xMnxSe的Tf高于Cd1-xMnxSe的Tf,用交换作用的理论作了讨论。
关键词: 相似文献
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通过X射线衍射和磁性测量等手段研究了(Nd1-xGdx)3Fe27.31Ti1.69(0≤x≤0.6)化合物的结构和磁性.X射线衍射测量结果表明Gd替代后并未改变Nd3(Fe,Ti)29化合物的晶体结构,但引起了晶胞体积收缩.随着Gd含量的增加,化合物的居里温度TC和室温磁晶各向异性场Ba单调增加,而自旋重取向
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1-xGdx)3Fe27.31Ti1.69化合物')" href="#">(Nd1-xGdx)3Fe27.31Ti1.69化合物
磁晶各向异性
自旋重取向
磁相图 相似文献
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通过对Eu2-xPbxRu2O7(x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0和1.8)系列样品的结构、电阻和磁化率的观测,结果发现,随着Pb替代浓度x值的增加,样品的电阻率逐渐减小,系统在x=0.8附近发生了金属-绝缘体(M-I)相变;Ru4+的局域磁矩及其自旋玻璃冻结温度TG也随之降低. 在该体系中,Pb2+对Eu3+的部分替代使样品中载流子浓度增加,Pb的6p能带与Ru 4d电子的T2g能带混合,能带得以拓宽,Ru 4d电子的巡游性增强,导致该体系物性的系列变化.
关键词:
自旋几何受挫
2-xPbxRu2O7体系')" href="#">Eu2-xPbxRu2O7体系
金属-绝缘体相变
自旋玻璃态 相似文献
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采用固相反应法,制备了不同成分的稀释磁性半导体Sn1-xMnxO 2(x=002,004,006).利用x射线衍射和傅里叶变换红外光谱法证明 了锰均匀地掺杂到二氧化锡中.在室温下研究了掺锰二氧化锡基稀释半导体的磁性,发现它具有明显的铁磁性 ,同时对磁性的强弱与锰的含量和烧结温度的关系作了研究.
关键词:
稀释磁性半导体
掺杂
烧结
铁磁性
1-xMnx O2')" href="#">Sn1-xMnx O2 相似文献
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研究了钙钛矿型锰氧化物La2/3Ca1/3Mn1-xTixO3(0≤x≤0.3)的结构、磁性和输运性质.发现Ti替代Mn强烈地抑制了La2/3Ca1/3MnO3的铁磁性和金属电导,并很大地提高了磁电阻值.在低掺杂情况下(x≤0.04),1%的Mn被Ti替代,居里温度TC和金属-绝缘体转变温度Tp分别平均下降了31和26.5K.当x=0.06时,铁磁态过渡为团簇玻璃态,并在x=0.20时完全变为自旋玻璃态.指出由于Ti的掺入而引起的磁稀释作用以及局域晶格畸变是产生上述结果的主要原因.
关键词: 相似文献
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K. Muraleedharan J.K. Srivastava V.R. Marathe R. Vijayaraghavan 《Journal of magnetism and magnetic materials》1985,49(3):333-336
The disordered spinel system, Zn0.5Co0.5FeCrO4 has been investigated using the low field magnetization and ac susceptibility measurements. From the present results it appears that this system orders into a cluster spin glass state with the magnetic moments of the ferrimagnetic clusters randomly frozen. Compared to the Ni and Co zinc ferrites with the same magnetic dilution, introduction of Cr into the B sites appears to increase the frustration and disorder dramatically. The predicted phase diagrams for the ordering in diluted magnetic spinels do not describe the magnetic behaviour of this system, presumably due to the disorder in the B sublattice in addition to the dilution in the A sublattice. 相似文献
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We have measured the critical temperature (Tc) and the upper critical magnetic field (Hc2) of La1-xGdxRu2. At low concentrations of the magnetic impurity (Gd), the suppression of Tc follows the expected Abrikosov-Gorkov (A-G) pair breaking curve. However, for larger concentrations, strong deviations below A-G are observed. Samples in this region (4. ? × ? 5. at. %) exhibit two Tc's. La1-xGdxRu2 is known to order magnetically, probably as a spin glass, and the magnetic ordering temperature (TM) has been measured in the normal state. This TM curve intersects the Tc curve in the concentration range where the Tc curve is re-entrant and we therefore attribute the re-entrant Tc behavior to the magnetic ordering of the Gd3+ ions. 相似文献
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The structural and magnetic properties of the mixed spinel Mg1+xMnxFe2-2xO4 system for 0.1<= x <= 0.9 have been studied by means of X-ray diffraction, magnetization, a.c. susceptibility and Mössbauer spectroscopy measurements. X-ray intensity calculations indicate that Mn4+ ions occupy only octahedral (B) sites replacing Fe3+ ions and the added Mg2+ ions substitute for A-site Fe3+ ions. All samples are magnetic at 12 K displaying Mössbauer spectra that have magnetic sextets coexisting with a central doublet that increases in population with increasing Mn concentration, indicating the presence of short range ordering (clustering). The Mössbauer intensity data show that Mn possesses a preference for the B-site of the spinel over the whole range of concentration. As expected, the hyperfine field and Curie temperature determined from a.c.susceptibility data decrease with increasing Mn content. Magnetization results indicate that on increasing dilution x, the collinear ferrimagnetic phase breaks down at x = 0.3 before reaching the ferrimagnetic percolation limit (x=0.6), as a result of the presence of competing exchange interactions, which is well supported by Mössbauer results. From all the above results, it is proposed that with increasing Mn content from x=0.6 to 0.9, the frustration and disorder increase in the system suppressing the ferrimagnetic ordering, and the system approaches to a cluster spin glass type of ordering at x=0.8 as reflected in the a.c.susceptibility and Mössbauer spectrum. 相似文献
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MAGNETIC PROPERTIES AND CRYSTALLIZATION OF THE RAPIDLY QUENCHED (Fe1-xNdx) 81.5B18.5 ALLOYS 总被引:1,自引:0,他引:1
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Magnetic properties and crystallization behaviors of amorphous (Fe1-xNdx) 81.5B18.5 alloys were studied. The crystallization temperature is found to rise at first and then drop monotonically with x, having a maximum value of 976K at x=0.11 (9at% Nd). The (Fe1-xNdx) 81.5B18.5 alloys prepared at a quenching rate of vs = 6.6m /s are amorphous, and exhibit good glass formability. Both the coercive field Hc and energy product (BH)max depend strongly on Nd concentration. Amorphous (Fe1-xNdx) 81.5B18.5 alloys with higher Nd concentration have a high coercive field at low temperature, due to the large random uniaxial anisotropy of Nd. The room-temperature Hc and (BH)max obtained on optimal annealing con-ditions show two maxima as a function of Nd concentration x. The highest room-temperature coercive field Hc =22 kOe within the Nd concentrations around x=0.368 and the maximum energy product(RH)max= 13.3 MG·Oe at x =0.055 are observed. The hard magnetic properties of these crystallized samples are related to the presence of the bard magnetic Nd2Fe14B phase. 相似文献
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Seisuke Nakashima Koji Fujita Atsuo Nakao Katsuhisa Tanaka Yasuhiko Shimotsuma Kiyotaka Miura Kazuyuki Hirao 《Applied Physics A: Materials Science & Processing》2009,94(1):83-88
We report on spatially selective change of magnetism from paramagnetic to ferrimagnetic-like behaviors in normal spinel ZnFe2O4 thin film under irradiation with 780 nm femtosecond laser pulses. The distribution of Zn2+ and Fe3+ ions in the irradiated region on the film surface becomes disordered because of local heating to high temperatures, and the
metastable phase of ZnFe2O4 is frozen in by the rapid quenching after irradiation, resulting in the formation of the ferrimagnetic phase. The ferrimagnetic
phase reverts to the paramagnetic state by annealing at 800°C. The present technique is useful for two-dimensional patterning
of magnetic thin films. 相似文献
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使用快速烧结和溶胶-凝胶方法制备了Bi(Fe1-xMnx)O3的块材陶瓷,其x能够达到0.3,因而可以得到较细的粉末. 经X射线衍射谱和拉曼光谱研究发现其结构转变取决于锰的掺杂浓度. 当x=0.05和0.1时,Bi(Fe1-xMnx)O3的结构保持斜方六面体结构;当x=0.3时,Bi(Fe1-xMnx)O3的结构变化到正方六面体结构.在x=0.05和0.1时观测到弱铁磁性,但在x=0.3时观测到强顺磁性. 这显示了Bi(Fe1-xMnx)O3从反铁磁性到顺磁性的磁相变,同时也表明其结构从R3C变化到C222. 在30和140 K, x=0.05和0.1时,观察到Bi(Fe1-xMnx)O3的两个反常现象. 在30 K时,直流磁记忆和缓慢测量Bi(Fe1-xMnx)O3团族的反常现象与冷冻的旋转玻璃系统有关. 相似文献