Eliezer Adar

Wire Machine Technologies Ltd., Israel

Magnetic metal-oxide microwires

Vítor Amaral

Universidade de Aveiro, Portugal

Mikalai Kalanda

Scientific and Practical Materials Research Centre of the NAS of Belarus, Belarus

Structure and magnetism of strontium ferromolybdate under conditions of the Fe and Mo cations ordering and oxygen nonstoichiometry

Vladislav Kataev

Leibniz-Institut für Festkörper- und Werkstoffforschung – IFW Dresden, Germany

Inversion of the Orbital States in the Intrinsically Stacked Oxide Sr2IrO4

A promising route to tailoring the electronic properties of quantum materials and devices rests on the idea of orbital engineering in multilayered oxide heterostructures. In this talk we will show that the interplay of interlayer charge imbalance and ligand distortions provides a knob for tuning the sequence of electronic levels even in intrinsically stacked oxides. We resolve in this regard the d-level structure of layered Sr2IrO4 by electron spin resonance (ESR) and ab initio quantum chemistry methods. Sr2IrO4 is a prototypical spin-orbital Mott insulator which has attracted considerable interest in the recent past. It has a rather simple crystalline structure displaying stacked, quasi two-dimensional IrO2 and double SrO layers.
Using ESR measurements at sub-THz frequencies in strong magnetic fields we were able to untangle the 5d-shell electronic structure of Sr2IrO4, in particular, the exact order of the Ir t2g levels. To do that, we have experimentally determined the spectroscopic g-tensor which appears inverted as compared to predictions of canonical ligand-field theory. The inversion of the g-tensor implies an inversion of the ordering of the t2g orbital states. This has been confirmed on the quantitative level by ab initio quantum chemistry methods which yielded experimentally observed g-factors. We show that in the layered structure of Sr2IrO4 a specific distribution of ionic charges between the IrO2 and SrO layers modifies the sequence of energy levels within the t2g and eg manifolds and consequently very fundamental physical properties such as the magnetic g-factors, which determine the relation between the magnetic moment and quantum number of a magnetic particle.
Given the nonpolar character of the metal-oxygen layers, our findings highlight the tetravalent transition-metal 214 oxides as ideal platforms to explore d-orbital reconstruction in the context of oxide electronics.

Dong-Hyun Kim

Chungbuk National University, Korea

Magnetization dynamics of ferromagnetic thin films over wide time scales

Magnetization dynamics of ferromagnetic thin films on a slower (~ sec) to a faster (~ fs) timescale will be presented. The ferromagnetic multilayer films such as Co/Pt and CoFeB/Pd as well as simple Co, Ni, Fe films will be explored by means of magneto-optical Kerr effect. On a slower time scale, minor hysteresis behavior will be presented, where corresponding microscopic magnetic domain patterns and domain dynamics are discussed together. On the other hand, photoinduced demagnetization/remagnetization behavior are examined on a faster time scale by means of time-resolved magneto-optical Kerr effect based on a femtosecond laser setup. Ultrafast signal of Kerr effect and reflectivity are fitted based on a 3-temperature model to analyze the temperatures of spin-, electron-, and lattice-subsystems. Fluence- and field-dependent ultrafast magnetization dynamics is experimentally investigated, where a separation of spin sub-system on a sub-ps time scale is found to lead to a giant magnetic cooling effect. Several other interesting topics will be discussed as well.

Andrii Korostil

Institute of Magnetism of the NAS of Ukraine and the MES of Ukraine, Ukraine

On controlled magnetization in nanoheterostructures

Controlling magnetization in magnetic nanoheterostructures at ultrafast time scales and ultrasmall space scales and ultra low power consumption is the top problem of the physics of magnetism, which has both fundamental scientific and applied significance with huge potential applications in novel magnetic devices. Utilizing the electronic spin degree of freedom creates new functionalities that lead to applications in information technologies such as sensors and memories. The magnetization control can be realized by different external fields possessing by corresponding mechanisms of the magnetization manipulation.
For the electromagnetic field, it is possible the mechanism of the effective bias field of the magneto-optic inverse Faraday effect and for magnetic with antiferromagnetic exchange interaction, the laser heating-induced mechanism associated with the effect of ferromagnetic-like transitional state. The electric field control can is realized via mechanism of the spin transfer torque exerting on localized magnetization states in the magnetic nanoheterostructures. Herewith, it is possible the voltage-controlled magnetic anisotropy, where the perpendicular magnetic anisotropy is controlled by the external gate voltage applied across a dielectric layer. In this case, the microscopic origin of the anisotropy change is attributed to voltage control by an effective interfacial Rashba spin-orbit coupling. In the conventional case, when the applied voltage involves current flow, the mechanism of the spin transfer torque is related to the electron spin polarization and the spin flow generated by the spin Hall effect.
Special attention is paid to features of the current spin-orbit induced magnetic dynamics in multilayer nanostructures with nonmagnetic heavy metal layers possessing by a strong spin-orbit interaction. These structures include ferromagnetic (antiferromagnetic AF)/normal metal nanostructures based on both conductive and insulating magnetics and heavy normal metals (e. g., FeCoB/Ta, YIG/Pt, Nio/Pt). The spin Hall effect of the conversion of an incoming charge current into a transverse (with respect to the charge current) spin current induces a spin-transfer torque and magnetic dynamics including a magnetic precession and switching. The magneto-dynamic effect of a spin current pumping generation together with the inverse spin Hall effect of conversion of the spin current into the incoming charge current provide the influence of the magnetic dynamics on the incoming charge current. These feedforward and feedback between the incoming charge current and the magnetic dynamics can be the basis for the spin-orbit driven self-sustained auto-oscillations of a magnetic order in the nanostructures. It is shown that these magnetic nanostructures possess by properties of controlled microwave radiation attaining tens THz in the antiferromagnetic case.

Ilya Kubasov

National University of Science and Technology “MISiS”, Russia

Bidomain lithium niobate crystals: technology, investigation, applications

Peter K. Petrov

Imperial College London, United Kingdom

Strain engineered properties of complex oxide thin films

Anatoli I. Popov

University of Latvia, Latvia

Carlos Rosário

Universidade de Aveiro, Portugal

Origin of the temperature and magnetic field dependence of the electrical transport in substoichiometric TaOx thin films

Gunnar Suchaneck

Technische Universität Dresden, Germany

Multi-target reactive sputter deposition of strontium ferromolybdate – Challenges and approaches

The deposition of Sr2FeMoO6 (SFMO) thin films with appropriate properties on silicon wafers is extremely difficult. This is caused by the formation of antisite defects of FeMo and MoFe even in stoichiometric films, the appearance of reduced phases, e.g. Fe, at lower and the SFMO decomposition into SrMoO4 and SrFeO3-x at too high oxygen partial pressure, respectively. The formation of oxygen vacancies narrows the available technology window additionally. On the other hand, the relatively high synthesis temperature of SFMO (ca. 1150 K) is not compatible with Si wafers already covered by oxide and electrode films.
Conventional RF sputtering using oxide targets comprising several cations suffer from different sputter yield of the constituents leading to the preferential sputtering phenomenon. Moreover, single phase SFMO ceramic targets exhibiting a low porosity and a homogeneous density are difficult to fabricate, particularly beyond diameters of 100 mm. They often crack during high-power sputtering due to local heating.
Multi-target reactive sputtering (MTRS) has the advantage to control the film stoichiometry, especially the Fe/Mo ratio of deposited thin films by process parameters like target power and substrate temperature. MTRS was carried out in a LS730S sputtering system (VON ARDENNE GmbH, Dresden, Germany). The computer- controlled system is equipped with a process chamber and a load-lock, both evacuated by turbo-molecular pumps. The process chamber consists of up to four 200 mm metal targets, two stationary radiation heaters and a wafer carousel holding four 150 mm silicon wafers. The base of the Fe target was directly connected with the RF (13.56MHz) generator. A unit for pulsed DC and arc suppression was connected between power supply and Mo target. Also, high-power-pulse sputtering was performed by connecting a switching unit between the DC power supply and either the Sr- or the Mo-target in order to increase the effective surface temperature by an additional energy flux from the low-pressure plasma. Base argon flow into the chamber was kept constant while an additional oxygen flow was carried directly to all three metal targets. The oxygen gas flow of one channel was controlled by a close-loop feedback circuit of a plasma emission monitor.
Film phase composition, texture, crystallite size and antisite disorder were characterized by XRD, film composition by EDX and XPS, and film microstructure by SEM and AFM. Electrical resistivity was measured by a standard four-point method carrying out switching the electric and magnetic fields directions. Magnetic and magnetotransport were obtained in the range of 4.2–300 K in constant magnetic fields of up to 8 T.
The results demonstrate that direct synthesis of SFMO by reactive multitarget sputtering is a promising technology for the fabrication of magnetoresistive devices operating at room temperature. However, the processing temperature should be adapted to the limits of silicon wafer technology. On the other hand, the narrow window of pure SFMO phase deposition requires a careful in-situ process control.

Sigitas Tamulevicius

Kauno Technologijos Universitetas, Lithuania

Technologies for 2-D nanostructures

Herman Terryn

Vrije Universiteit Brussel, Belgium

Advanced Characterization to Study Early nucleation and Growth Electrodeposition Mechanisms in Aqueous and Non Aqueous Electrolytes

Maxim Varenik

Weizmann Institute of Science, Israel

Van Vleck paramagnetism and sign-reversal of magnetostriction in non-magnetic materials with cubic symmetry