The magnetic behaviour of SmN has been investigated in stoichiometric polycrystalline films. All samples show ferromagnetic order with Curie temperature (T_c) of 27 +/- 3 K, evidenced by the occurrence of hysteresis below T_c. The ferromagnetic state is characterised by a very small moment and a large coercive field, exceeding even the maximum applied field of 6 T below about 15 K. The residual magnetisation at 2 K, measured after cooling in the maximum field, is 0.035 mu_B per Sm. Such a remarkably small moment results from a near cancellation of the spin and orbital contributions for Sm3+ in SmN. Coupling to an applied field is therefore weak, explaining the huge coercive field . The susceptibility in the paramagnetic phase shows temperature-independent Van Vleck and Curie-Weiss contributions. The Van Vleck contribution is in quantitative agreement with the field-induced admixture of the J=7/2 excited state and the 5/2 ground state. The Curie-Weiss contribution returns a Curie temperature that agrees with the onset of ferromagnetic hysteresis, and a conventional paramagnetic moment with an effective moment of 0.4 mu_B per Sm ion, in agreement with expectations for the crystal-field modified effective moment on the Sm3+ ions.
Towards a Fully Ab-Initio Description of the Diluted Magnetic Semiconductor $Ga_{1-x}Mn_{x}As$. Ferromagnetism, Electronic Structure, and Optical Response
Tunability of Room Temperature Ferromagnetism in Spintronic Semiconductors through Non-magnetic Atoms
通过在半导体晶格中添加磁性原子来实现和控制室温铁磁性（RTFM）是近十年来固态物理中最重要的问题之一。在这里，我们报告的第一次，据我们所知，在机制上，允许RTFM被调谐的列入\emph{non-magnetic}铝镍铁氧体。这种材料，NiFe $_{2-x}$ Al $_x$ O $_4$（x=0，0.5，1.5），已经显示出磁性半导体技术的前景，我们能够增加其多功能性的技术可行性与我们的结果。Fe原子（Fe $^{3+}$ T $_d$、Fe $^{2+}$ O $_h$和Fe $^{3+}$ O $_h$）的位置占有率和价态可以通过包含铝而有系统地控制。利用铝强烈偏好3+八面体环境的事实，我们可以选择性地用铝原子填充铁位点，从而专门调整每个铁位点的磁性贡献，因此也调整了块体材料的磁性贡献。有趣的是，铝对电子结构（补充材料）的影响很弱，允许人们在保持理想的电子特性的同时实现理想的磁特性。
X-ray Anomalous Scattering of Diluted Magnetic Oxide Semiconductors: Possible Evidence of Lattice Deformation for High Temperature Ferromagnetism
我们研究了在金红石型和金红石型Ti_{1-x} $Co$ _{x} $O$ _{2-delta} $ thin films that exhibit room-temperature ferromagnetism. Intensities of the x-ray Bragg reflection from the films were measured around the $ K $-absorption-edge of Co. If the Co ions randomly substitute on the Ti sites, the intensity should exhibit an anomaly due to the anomalous dispersion of the atomic scattering factor of Co. However, none of the anatase and rutile samples did exhibit an anomaly, unambiguously showing that the Co ions in Ti$ _{1-x} $Co$ _{x} $O$ _{2-delta} $ are not exactly located at the Ti sites of TiO$ _2 $. The absence …
Ba(Zn,Co)2As2: a II-II-V Diluted Ferromagnetic Semiconductor with N-type Carriers
稀释铁磁半导体结合了半导体的铁磁性，在自旋敏感电子学（自旋电子学）器件中具有潜在的应用。在III-V（Ga，Mn）As薄膜中观察到铁磁有序后，对DMS材料的研究爆炸了。最近，一系列与铁基超导体同构的DMS化合物被报道。其中，（Ba，K）（Zn，Mn）$T_C$的最高居里温度为230 K。然而，大多数DMS，包括（Ga，Mn）As，是p型的，即，介导铁磁性的载流子是空穴。对于实际应用，具有n型载流子的DMS也是有利的。本文报道了一种具有n型载流子的II-II-V稀磁半导体Ba（Zn，Co）$_2$ As $_2$的成功合成。磁化强度测量表明，在$T_{C} \sim$ 45 K时发生铁磁转变.霍尔效应和塞贝克效应的测量共同证实，占主导地位的载流子是电子。利用体积灵敏磁探针μ子自旋弛豫（$μ$ SR），我们还证实了Ba（Zn，Co）$_2$ As $_2$的铁磁性是本征的，内场是静态的。
Comparison between ab-initio and phenomenological modeling of the exchange couplings in diluted magnetic semiconductors: the case of $Zn_{1-x}Cr_{x}Te$
