Sawicki Bogdan, Tomaszewicz Elżbieta, Groń Tadeusz, Oboz Monika, Kusz Joachim, Berkowski Marek
Institute of Physics, University of Silesia, Katowice 40-007, Poland.
Faculty of Chemical Technology and Engineering, Department of Inorganic and Analytical Chemistry, West Pomeranian University of Technology, Szczecin 70-310, Poland.
ACS Omega. 2023 Oct 2;8(41):38459-38468. doi: 10.1021/acsomega.3c05253. eCollection 2023 Oct 17.
Single crystals of CaMn□Nd(MoO)(WO) molybdato-tungstates (□ denotes vacant sites) with a scheelite-type structure have been successfully grown by the Czochralski technique in an inert atmosphere. This paper presents the results of structural, optical, magnetic, and electrical properties, as well as the broadband dielectric spectroscopy measurements of single crystals with different Nd ion concentrations, , when = 0.0050 or = 0.0098, and with constant content of Mn ions, , when = 0.0050. Our magnetic studies have shown that substitution of diamagnetic Ca ions in the CaMoO matrix with paramagnetic Nd ones with a content not exceeding 0.02 and having a screened 4f-shell revealed a significant effect of orbital diamagnetism and Van Vleck's paramagnetism. Both single crystals have revealed residual electrical conductivity without an intrinsic region and a change of sign of the Seebeck coefficient at ca. 230 K. Dielectric spectroscopy measurements have shown constant values of relative permittivity (ε ∼ 8) and loss tangent (tan δ ∼ 0.01) both up to 400 K and up to 1 MHz, as well as the Fermi energy (∼0.04 eV) and the Fermi temperature (∼500 K) determined for both crystals from the diffusion component of thermopower. These results suggest the presence of shallow acceptor and donor levels in the studied crystals.
采用提拉法在惰性气氛中成功生长出具有白钨矿型结构的钼酸钨酸钙锰钕（CaMn□Nd(MoO)(WO)，□表示空位）单晶。本文介绍了不同钕离子浓度（当(x = 0.0050)或(x = 0.0098)）且锰离子含量恒定（当(y = 0.0050)）的单晶的结构、光学、磁性和电学性质以及宽带介电谱测量结果。我们的磁性研究表明，在CaMoO基体中用含量不超过0.02且具有屏蔽4f壳层的顺磁性钕离子取代抗磁性钙离子，揭示了轨道抗磁性和范弗莱克顺磁性的显著影响。两种单晶均显示出无本征区的残余电导率以及在约230 K时塞贝克系数符号的变化。介电谱测量表明，在高达400 K和高达1 MHz的频率范围内，相对介电常数（(\varepsilon \sim 8)）和损耗角正切（(\tan \delta \sim 0.01)）均为恒定值，并且根据热功率的扩散分量确定了两种晶体的费米能量（(\sim 0.04) eV）和费米温度（(\sim 500) K）。这些结果表明在所研究的晶体中存在浅受主和施主能级。
