SrRuO $_3$在4种$d$基氧化物中呈现出罕见的铁磁性。虽然大多数人认为SrRuO $_3$中的磁性状态是巡游型的，但最近的研究表明这种材料中的磁性是巡游和局域化模型共存的。本文采用修正的Arrott图、Kouvel-Fisher图和临界等温线分析等方法研究了掺杂SrRu $_{1-x}$ Ti $_x$ O $_3$在磁转变温度$T_c$范围内的临界行为，研究了磁态的演化.用Ti的$^{4+}$（3 $d^{0}$）取代Ru的$^{4+}$（4 $d^4$），除了改变费米能级的电子关联效应和态密度外，只会稀释磁性系统。令人惊讶的是，$T_c$不随$x$而改变。此外，我们的分析表明，与自发磁化强度相关的指数$β$增加，而与初始逆磁化率和临界磁化强度相关的指数$γ$和$δ$分别随着Ti的替代而降低。估计的指数与任何已建立的普适类理论模型都不匹配，但指数服从Widom关系和标度行为。有趣的是，在本系列中的指数的这种特殊的演变与等电子掺杂的Sr $_{1-x}$ Ca $_x$ RuO $_3$中的相似。我们认为，现场稀释钛导致形成磁簇，导致这种特定的变化的临界指数。
英文摘要：
SrRuO$_3$ presents a rare example of ferromagnetism among the 4$d$ based oxides. While the nature of magnetic state in SrRuO$_3$ is mostly believed to be of itinerant type, recent studies suggest a coexistence of both itinerant and localized model of magnetism in this material. Here, we have investigated the evolution of magnetic state in doped SrRu$_{1-x}$Ti$_x$O$_3$ through studying the critical behavior using standard techniques such as, modified Arrott plot, Kouvel-Fisher plot and critical isotherm analysis across the magnetic transition temperature $T_c$. The substitution of nonmagnetic Ti$^{4+}$ (3$d^{0}$) for Ru$^{4+}$ (4$d^4$) would simply dilute the magnetic system apart from modifying the electron correlation effect and the density of states at Fermi level. Surprisingly, $T_c$ does not change with $x$. Moreover, our analysis show the exponent $β$ related to spontaneous magnetization increases while the exponents $γ$ and $δ$ related to initial inverse susceptibility and critical magnetization, respectively decrease with Ti substitution. The estimated exponents do not match with any established theoretical models for universality classes, however, the exponent obey the Widom relation and the scaling behavior. Interestingly, this particular evolution of exponents in present series has similarity with that in isoelectronic doped Sr$_{1-x}$Ca$_x$RuO$_3$. We believe that site dilution by Ti leads to formation magnetic clusters which causes this specific changes in critical exponents.
SrRuO3 (SRO) is an itinerant ferromagnet with strong coupling between the charge, spin, and lattice degrees of freedom. This strong coupling suggests that the electronic and magnetic behaviors of SRO are highly susceptible to changes in the lattice distortion. Here we show how the spin interaction and resultant magnon formation change with the modification in the crystallographic orientation. We fabricated SRO epitaxial thin films with (100), (110), and (111) surface orientations, to systematically modulate the spin interaction and spin dimensionality. The reduced spin dimensionality and enhan…
Localized-itinerant dichotomy and unconventional magnetism in SrRu$_2$O$_6$
电子关联倾向于产生局部磁矩，如果晶格不太受挫折，这些磁矩通常是有序的。六方晶系化合物SrRu $_2$ O $_6$具有相对高的Neel温度，但局部磁矩较小，这似乎与$t_{2g}^3$构型中Ru $^{5+}$的标称价态不一致。本文采用密度泛函理论（DFT）结合动态平均场理论（DMFT）研究了SrRu $_2$ O $_6$的电子性质。我们发现，Ru $d$和O $p$状态之间的强杂化导致Ru价更接近$+4$，导致小有序矩$\sim1.2μ_B$。虽然这是一致的DFT预测，相关效应被发现发挥重要作用。在整个温度范围内，Ru原子的局部磁矩为有限的$\sim2.3μ_B$.由于较低的对称性，$t_{2g}$流形被分裂，准粒子重量在$a_{1g}$态中被重正化，而在$e_g'$态中的重正化大约弱2- 3倍。我们的理论Neel温度$\sim700$ ~K与实验观测值相当吻合。SrRu $_2$ O $_6$是一个独特的系统，其中本地化和巡回电子共存，接近轨道选择性莫特跃迁内的$t_{2g}$部门。
Here, we study the electrical transport and specific heat in 4$d$ based ferromagnetic material SrRuO$_3$ and its Ti substituted SrRu$_{1-x}$Ti$_x$O$_3$ series ($x$ $\le$ 0.7). The SrRuO$_3$ is a metal and shows itinerant ferromagnetism with transition temperature $T_c$ $\sim$ 160 K. The nonmagnetic Ti$^{4+}$ (3$d^0$) substitution would not only weaken the active Ru-O-Ru channel but is also expected to tune the electronic density and electron correlation effect. A metal to insulator transition has been observed around $x$ $\sim$ 0.4. The nature of charge transport in paramagnetic-metallic state…
Critical current measurements in superconductor - ferromagnet - superconductor junctions of $YBa_2Cu_3O_y$-$SrRuO_3$-$YBa_2Cu_3O_y$: No evidence for a dominant proximity induced triplet superconductivity in the ferromagnetic barrier
We have studied the magnetic properties of pressure-induced ferromagnet Ca2RuO4 to reveal the uniqueness of the 4d-electron ferromagnetism in the quasi-two-dimensional conductor. The magnetic parameters have been estimated from the paramagnetic susceptibility and the magnetisation process under pressure up to 2 GPa. The parameters can well be interpreted on the basis of the self-consistent renormalization theory of spin fluctuation for 3D-itinerant ferromagnet. Nevertheless, the metallic Ca2RuO4 shows quite strong anisotropy not only in the conductivity but also in the magnetisation process. S…
We developed a framework for directly calculating the spin susceptibility of anisotropic itinerant ferromagnets in the full temperature range within the coherent potential approximation in the disordered local moment picture. As a test of our formulation, we demonstrate the computation for the temperature ($T$) dependence of the spin susceptibility for Rashba-type ferromagnets with the Curie temperature $T_\mathrm{C}$. In a certain parameter, we found that the inverse transverse susceptibility $1/χ_\perp\simeq\mathrm{const.}$ for $T<T_\mathrm{C}$ and $1/χ_\perp\propto T-T_\mathrm{C}$ for $T>T_…
We report Electron Spin Resonance of the itinerant ferromagnets LaCrGe3, CeCrGe3, and PrCrGe3. These compounds show well defined and very similar spectra of itinerant Cr 3d spins in the paramagnetic temperature region. Upon cooling and crossing the Cr-ferromagnetic ordering (below around 90 K) strong spectral structures start to dominate the resonance spectra in a quite different manner in the three compounds. In the Ce- and Pr-compounds the resonance is only visible in the paramagnetic region whereas in the La-compound the resonance can be followed far below the ferromagnetic ordering tempera…
We theoretically investigated magnetocrystalline anisotropy (MA) at a finite temperature $T$ in ferromagnetic metals. Assuming a Rashba-type ferromagnet with uniaxial MA, we defined the MA constants $K_\mathrm{u}(T)$ derived from several different concepts. Our purpose was to examine the equality between them and to confirm a power law between $K_\mathrm{u}(T)$ and magnetization $M(T)$ in the form of $K_\mathrm{u}(T)/K_\mathrm{u}(0)=[M(T)/M(0)]^α$. We demonstrate that $α$ equals 2 in the itinerant-electron limit and increases with the localized feature of electrons passing through $α=3$, predi…
Heavy fermion (HF) states emerge in correlated quantum materials due to the interplay between localized magnetic moments and itinerant electrons, but rarely appear in 3d-electron systems due to high itinerancy of d-electrons. Here, an anomalous enhancement of Kondo screening is observed at the Kondo hole of local Fe vacancies in Fe3GeTe2 which is a recently discovered 3d-HF system featuring of Kondo lattice and two-dimensional itinerant ferromagnetism. An itinerant Kondo-Ising model is established to reproduce the experimental results which provides insight of the competition between Ising fer…
Perovskite SrRuO$_3$ is a prototypical itinerant ferromagnet which allows interface engineering of its electronic and magnetic properties. We report synthesis and investigation of atomically flat artificial multilayers of SrRuO$_3$ with the spin-orbit semimetal SrIrO$_3$ in combination with band-structure calculations with a Hubbard $U$ term and topological analysis. They reveal an electronic reconstruction and emergence of flat Ru-4d$_{xz}$ bands near the interface, ferromagnetic interlayer coupling and negative Berry-curvature contribution to the anomalous Hall effect. We analyze the Hall ef…
