首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 62 毫秒
1.
闫羽  金汉民 《物理学报》2000,49(7):1362-1365
基于单离子晶场模型,提出了计算稀土-Fe(Co)金属间化合物取向多晶样品磁化曲线的方法.用此方法计算了取向Pr2Fe14B和Nd2Fe14 B多晶的高场磁化曲线,计算中使用了拟合化合物单晶磁化曲线得到的交换场与晶场参数.计 算曲线与实验曲线相符合. 关键词: 磁化曲线 晶场 2Fe14B')" href="#">R2Fe14B  相似文献   

2.
在GdoBr∶Eu的常压和高压荧光谱实验数据基础上,对晶场能级及其重心进行了拟合计算,得到了晶场参数和自由离子参数(Slater参数和自旋 轨道耦合参数)在高压下的变化情况.计算结果表明,随压力增大,晶场参数B40,B60增大,B64减小,B20,B44的变化有些起伏.晶场强度在8GPa以 关键词:  相似文献   

3.
本文根据晶场理论计算了α-Fe2O3的单离子磁晶各向异性。采用点电荷模型,计及近邻及次近邻对晶场的贡献,并考虑到近邻O2-离子对次近邻Fe3+离子的电屏蔽效应,在六级微扰近似下,得到单离子各向异性场Hsi=102.3×102Oe。这一结果结合Artman等人对磁偶极各向异性的计算,导出了α-Fe2O3的Morin转变温度T 关键词:  相似文献   

4.
李华  姜寿亭  梅良模  高汝伟 《物理学报》1993,42(7):1179-1185
本文根据Nd2Fe14B化合物中存有少量巡游电子的基本实验事实,提出了在Nd2Fe14B中配位子所产生的晶场和巡游电子所产生的电场共同造成了Nd离子磁晶各向异性的理论模型。提出并解决了计算巡游电子同中心Nd离子相互作用的理论方法。在同时考虑Nd离子所受配位子的晶场和巡游电子的电场的作用情况下,用单离子模型计算了Nd2Fe14B中Nd离子所产生的磁晶各向异性及其随温度的变化。所 关键词:  相似文献   

5.
夏天  张国营  张学龙  薛刘萍 《物理学报》2007,56(3):1741-1745
研究了晶场二级效应在PrF3晶体中的作用,发现该效应可使Pr3+离子的晶场单态与其他态混合,对PrF3晶体磁化率产生明显影响.进一步研究了晶体内的交换作用有效场,其形式为Hin=(1.9-0.02556T)×10-5M,在100—300 K的温度范围内,以此计算的PrF3晶体的倒数磁化率和Verdet常数的倒数与实验值符合较好.结果表明,在PrF3晶体中,晶场二级效应与离子间的交换作用都不能忽略. 关键词: 晶场二级效应 交换作用有效场 Verdet常数 3晶体')" href="#">PrF3晶体  相似文献   

6.
作为文献[4]的自然推广,本文讨论了低对称性(C4v或D4h,C3v或D3h)晶场中3d5离子零场劈裂常数D值的计算。给出D值依赖于Racah参数、晶场参数和自旋-轨道耦合常数ξ的表示式。用于α-Al2O3晶体中Fe3+,离子D值的计算,结果与实验值能够较好地符合。 关键词:  相似文献   

7.
杨桂林  徐游  卢德林  翟宏如 《物理学报》1986,35(9):1142-1147
本文对NaCl型结构的稀土化合物RX(X=N,P,As,Sb,Bi)的晶场参数B40的实验值进行了分析。在此基础上我们提出一个新的利用简单点电荷模型计算RX晶场参数B40值的关系式:B40=k3(B40)p+c3。用此关系式我们确定了一系列RX的晶场参数B40值,结果与实验值符合很好。对关系式的含义本文也作了充分讨论。 关键词:  相似文献   

8.
陈宪锋 《物理学报》2005,54(8):3856-3861
针对低温下各向同性Pr2Fe14B永磁材料的最小形核场问题,用数值 计算法和近似解 析解研究了第二磁晶各向异性常数K2对最小形核场的影响.研究发现,尽管对于 Nd2 Fe14B永磁材料一级近似的解析解与数值计算结果很接近,但是对于低温下各向 同性P r2Fe14B永磁材料则至少要用二级近似下的解析解才能与数值计算 结果相接近.用有 关最小形核场的计算结果很好地解释了低温时各向同性Pr2Fe14B永 磁材料的矫顽力与最小形核场的关系. 关键词: 第二磁晶各向异性常数 形核场 矫顽力  相似文献   

9.
黄逸佳  张国营  胡风  夏往所  刘海顺 《物理学报》2014,63(22):227501-227501
在一些磁性材料内, 磁性离子间交换作用和磁性离子的自旋涨落对材料磁性有影响. 本文根据磁比热实验值确定了晶场参数后, 利用包含自旋涨落的交换作用有效场Hm= n0 (1 + γ T + β eω T)M, 计算了PrNi2晶体晶场能级的Zeeman劈裂. 在温度为3.8 K ≤T≤ 30 K范围内, 计算了该晶体多晶磁矩随外磁场的变化, 以及外磁场H=5000 Oe时磁化率倒数随温度的变化, 计算结果和实验值符合较好. 当外磁场在0–50000 Oe时, 计算的该晶体的磁熵变与已有文献的理论结果相似. 计算结果说明, 提出的包含自旋涨落的交换作用有效场不仅适合亚铁磁性晶体, 而且也适合顺磁性晶体. 关键词: 2')" href="#">PrNi2 磁比热 交换作用有效场 磁矩 磁熵变  相似文献   

10.
通过选择激发SBN晶体中处于不同晶场位的Eu3+离子,得到5D07F1的时间分辨荧光光谱,确定了不等价晶场位的离子间的能量转移速率。荧光峰随激发波数的变化表明局部晶场的连续畸变。 关键词:  相似文献   

11.
Neutron spectroscopy has been employed to study the crystal-field excitations in Pr2CuO4. The energetic ordering of the crystal-field levels and the crystal-field parameters are determined from the observed transitions. Our results are consistent with the large magnetic anisotropy observed in single-crystal susceptibility data.  相似文献   

12.
Inelastic neutron scattering experiments have been performed in UBr3 in order to determine the crystal-field levels. Four transitions between the ground state and all excited states have been observed, thus the crystal-field level scheme could be unambigously assigned. The Russell-Saunders coupling scheme has been used to derive the crystal-field parameters which cannot be accounted for by a simple point charge calculation.  相似文献   

13.
The crystal-field model is applied to a series of scheelites crystals (CaWO4, SrWO4, PbWO4, BaWO4, CdMoO4, CaMoO4, SrMoO4 and PbMoO4) doped with the Yb3+ ion. The calculated crystal-field parameters present a general trend of variation with M2+ ionic radius of the host cation. The maximum splitting ΔE of the 2F7/2 manifold of the Yb3+ ion is then obtained as a function of NV crystal-field strength parameters. The agreement between experimental results and theoretical predictions for all investigated systems is very satisfactory. The crystal-field effects are very important for the prediction of emission energies of the Yb3+ ion in different scheelites.  相似文献   

14.
The crystal structural parameters of Nd 3+-doped rare earth orthotantalate Gd x Lu 1 x TaO 4(x = 0.85) are determined by applying the Rietveld refinement to its X-ray diffraction,and its emission and excitation spectra at 77 K are analysed.The relativistic model of ab initio self-consistent DV-Xα method,which is applied to the cluster NdO 8 in Gd x Lu 1 x TaO 4,and the effective Hamiltonian model are used to investigate its spin-orbit and crystal-field parameters.The free-ions and crystal-field parameters are fitted to the experimental energy levels at 77 K with a root-mean-square deviation of 14.92 cm 1.According to the crystal-field calculations,96 levels of Nd 3+ are assigned.Finally,the fitting results of free-ions and crystal-field parameters are compared with those already reported for Nd 3+:YAlO 3.The results indicate that the free-ion parameters are similar to those of the Nd3+ in Gdx Lu1-x TaO4 and YAlO 3 hosts,and the crystal-field interaction of Nd3+ in Gdx Lu1-x TaO4 is stronger than that in YAlO 3.  相似文献   

15.
The specific heat of CeCu6–x Au x withx=0,0.3, and 0.9, and of the corresponding La homologues has been measured between 1.5 K and 150 K. With increasingx we find progressively better-defined Schottky anomalies arising from the crystal-field splitting, which is attributed to the decrease of the Kondo temperature. Both observations are in line with the results of inelastic neutron-scattering data performed on samples withx=0.5. Overall, the crystal-field splitting does not change very much upon alloying with Au. A detailed analysis shows that forx=0.5 the quasielastic line width is smaller and the inelastic crystal-field transitions are better resolved compared to CeCu6.  相似文献   

16.
We present an infrared crystal-field study of Pr2CuO4 single crystals and thin films. Excitations from the ground state multiplet 3H4 to the 3H5, 3H6, 3F2 and 3F3 excited multiplets are observed in both single crystals and thin films. A precise set of crystal-field parameters, that reproduces the energy and the symmetry of the levels, is determined. Received 25 April 2001  相似文献   

17.
The optical isotropy of the cubic garnet was overcome by crystal-site selective excitation and fluorescence spectroscopy. Thus the symmetries of the crystal-field states of the free ion levels7F J and5D4 could be determined. On this basis a crystal field analysis was performed to derive the crystal-field parameters for the Tb3+ ions replacing the Y3+ ions on the D2 sites.  相似文献   

18.
The g factor of Cr4+ in Y2SiO5 crystal is calculated from a completed high-order perturbation formula, in which not only the conventional contribution to the g-shift Δg(=gge) from the crystal-field mechanism, but also the contribution from the charge-transfer mechanism (which is neglected in the crystal-field theory) are considered. The calculated result shows good agreement with the observed value. It is found that the calculated Δg due to the charge-transfer mechanism is opposite in sign and about 38% in magnitude, compared with that due to the crystal-field mechanism. So, in the studies of the g factor for a 3dn ion having high valence state in crystals, the contribution due to the charge-transfer mechanism should be taken into account.  相似文献   

19.
Using a crystal-field calculation within a point charge model, we interpret the rare-earth magnetic moment direction in the equiatomic rare earth-silicon compounds of CrB type. We showed that the 2nd order crystal-field parameter V22 is predominant and implies the magnetic moment to the perpendicular to the two-fold quantization axis i.e. b-axis. The calculated magnetic moment direction are in good agreement with neutron diffraction results.  相似文献   

20.
Ab initio calculations using an extended set of gaussian-type orbitals have been performed for the CoO6 10- cluster in the Hartree-Fock approximation and with a limited configuration interaction. The results have been compared with those of crystal-field theory. CoO is found to be a very ionic system with localized d-electrons. The excited d-states may be described using a simple configuration interaction scheme, which is found to be almost equivalent to a crystal-field parameterized configuration interaction built on Hartree-Fock results. Localization and delocalization phenomena in openshell systems have been discussed.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号