Phase transition observation in Weyl semimetal candidate Mn3Ga epitaxial thin films evidenced by transverse magnetoresistance

Critical current properties in YBCO coated IBAD tapes

The effect of Ga and Co doping on the hopping transport of electrons in ZnO films was studied. All investigated films were deposited on monocrystalline substrates by water assisted metal organic chemical vapour deposition method. Temperature dependencies of the resistivity of all films obeyed the Mott's law at low temperatures. Both positive and negative magnetoresistance were observed in the temperature range of the Mott's law. The values of the localization length obtained from magneto transport data for ZnO and ZnO:Ga films are larger than the effective Bohr radii of a shallow donor state and are independent on the Ga content. These observations point to the localization of electrons in the random potential originating from the structural disorder. In Co doped ZnO films large positive magnetoresistance was observed in low magnetic fields at low temperatures. The value of positive magnetoresistance increases with an increase of Co content and decrease of temperature. Observed magneto transport properties of Co-doped films were interpreted by the decrease of electron hopping probability due to decrease of the density of localized states in magnetic field.

Magnetic nano‐objects, namely antiskyrmions and Bloch skyrmions, have been found to coexist in single‐crystalline lamellae formed from bulk crystals of inverse tetragonal Heusler compounds with D2d symmetry. Here evidence is shown for magnetic nano‐objects in epitaxial thin films of Mn2RhSn formed by magnetron sputtering. These nano‐objects exhibit a wide range of sizes with stability with respect to magnetic field and temperature that is similar to single‐crystalline lamellae. However, the nano‐objects do not form well‐defined arrays, nor is any evidence found for helical spin textures. This is speculated to likely be a consequence of the poorer homogeneity of chemical ordering in the thin films. However, evidence is found for elliptically distorted nano‐objects along perpendicular crystallographic directions within the epitaxial films, which is consistent with elliptical Bloch skyrmions observed in single‐crystalline lamellae. Thus, these measurements provide strong evidence for the formation of noncollinear spin textures in thin films of Mn2RhSn. Using these films, it is shown that individual nano‐objects can be deleted using a local magnetic field from a magnetic tip and collections of nano‐objects can be similarly written. These observations suggest a path toward the use of these objects in thin films with D2d symmetry as magnetic memory elements.

This paper reports on an abnormally high Curie temperature ( $T_{c}$ ) of a Pb(Mg1/3, Nb2/3)O3-PbTiO3 (PMN-PT) epitaxial thin film on Si prepared by sputter deposition with fast cooling. This deposition method was previously applied to Pb(Mn, Nb)O3-Pb(Zr, Ti)O3, and a c-axis-oriented epitaxial film with high $T_{c}$ was obtained. Using the same method, a crack-free 2- $\mu \text{m}$ -thick PMN-PT thin film was epitaxially grown on a Si substrate covered with buffer layers. The piezoelectricity, $\vert \text{e}_{31,f}\vert $ , was as large as 18~19 C/m2 under an electric field ranging from 25 to 75 kV/cm. The temperature characteristics of the dielectric constant and crystalline structure were significantly different from those of a bulk single crystal of PMN-PT, and suggested $T_{c}$ higher than 500 °C. The enhanced $T_{c}$ was possibly caused by thermally induced compressive strain received from the Si substrate. This approach can be an effective method for breaking the well-known tradeoff relationship between piezoelectricity and $T_{c}$ of a piezoelectric thin film. 0.

The interface of epitaxial (Pb0.35Sr0.65)TiO3 films on MgO substrates grown by pulsed laser ablation was studied using transmission electron microscopy (TEM). Cross-section TEM studies revealed that the epitaxial films have a lattice mismatch of −6.2% with respect to the substrates. Electron diffraction pattern and high-resolution TEM image of the plan-view (Pb0.35Sr0.65)TiO3∕MgO interface present evidence of a modulated structure on the film plane. This allowed obtaining the actual lattice mismatch of −7.14% at the interface. Plan-view TEM of the interface is able to provide fundamental information that cannot be obtained by the cross-section TEM alone, and its advantages in studying such epitaxial films are addressed.

Epitaxial thin films can offer unprecedented definition of an electrocatalyst surface, defining the crystallographic orientation, interaction with a current collector, and providing an atomically flat surface for quantitative spectroscopy yielding mechanistic insights. This review introduces experts in thin films to the important parameters of electrochemical setups, techniques, and methods for quantifying electrocatalytic activity and comparing it across the literature. Examples are drawn from the literature measuring oxygen electrocatalysis on epitaxial oxide thin films. We share best practices in the robust measurement of intrinsic activity of thin films, including methods of electrical contact and assessment of charge transport in situ. We conclude by highlighting recent insights from epitaxial films in understanding oxygen electrocatalysis.

Polarized neutron grazing incidence diffraction on magnetic epitaxial thin films

Post-annealed epitaxial thin films of TlBa{sub 2}CaCu{sub 2}O{sub x} (Tl-1212) have been fabricated using sputtered precursors. Values of the transport critical current (J{sub c}) for Tl-1212 epitaxial thin films in magnetic fields up to 7 tesla and at temperatures ranging from 25 to 77K are reported. These values are compared with those for Tl-2212 epitaxial films, Tl-2212 polycrystalline films, and Tl-1223 polycrystalline duck films. This comparison explicitly demonstrates the roles of grain boundaries and anisotropy in limiting the transport J{sub c}. Analysis also supports the existence of a universal pinning defect in every highly anisotropic high-temperature superconductor, with a lower bound on the size of the defect being approximately 12{Angstrom} in diameter.

ABSTRACTWe report the direct measurement of elastic strain effect on the electrical and magnetic properties of single domain epitaxial SrRuO3 thin films, using a lift-off technique. The as-grown films on vicinal (001) SrTiO3 substrates are subjected to elastic biaxial compressive strain within the plane and tensile strain normal to the plane. In contrast, the lift-off films prepared by chemical etching of SrTiO3 substrates, are completely strain free with bulk like lattice. Our measurements indicate that the elastic strain can significantly affect the electrical and magnetic properties of epitaxial ferromagnetic SrRuO3 thin films. For the strained films, the Curie temperature (Tc) was suppressed to 150K and the saturation magnetic moment (Ms) was decreased to 1.15μB/Ru atom as compared to a Tc of 160K and Ms of 1.45μB/Ru atom for the strain free films. These property changes are attributed to the structural distortion due to the elastic strain in the as-grown epitaxial thin films. Our results provide direct evidence of the crucial role of lattice strain in determining the properties of the perovskite epitaxial thin films.

Although there is considerable interest in BiFeO3 owing to its versatile physical properties, which make it suitable for a wide range of applications, its high leakage current is a significant limitation. Among various methods for reducing the leakage current, substitution with transition-metal or rare-earth elements is widely recognized as the most effective approach. Herein, to enable in-depth studies of the physical properties of BiFeO3, high-quality epitaxial BiFeO3 thin films with a low leakage current must be formed. However, owing to the difficulty of controlling the element doping when pulsed laser deposition is used for epitaxial thin-film growth, studies on substitutional doping based on epitaxial BiFeO3 thin films have not been systematically carried out. In this regard, we establish an innovative approach for overcoming the high leakage current of BiFeO3 by fabricating artificially engineered superlattice-based epitaxial BiFeO3 thin films in which there is a significant reduction of the leakage current. The control of the element doping in epitaxial BiFeO3 thin films is easily regulated precisely at the atomic-scale level. The results of this study strongly suggest that superlattice-based epitaxial BiFeO3 thin films can be a cornerstone for exploring the reliable fundamental physical properties of substitutional doping in epitaxial BiFeO3 thin films.

By lifting an epitaxial thin film off its growth substrate, we directly and quantitatively demonstrate how elastic strain can alter the magnetic and electrical properties of single-domain epitaxial SrRuO3 thin films (1000 Å thick) on vicinal (001) SrTiO3 substrates. Free-standing films were then obtained by selective chemical etching of the SrTiO3. X-ray diffraction analysis shows that the free-standing films are strain free, whereas the original as-grown films on SrTiO3 substrates are strained due to the lattice mismatch at the growth interface. Relaxation of the lattice strain resulted in a 10 K increase in the Curie temperature to 160 K, and a 20% increase in the saturation magnetic moment to 1.45 μB/Ru atom. Both values for the free-standing films are the same as that of the bulk single crystals. Our results provide direct evidence of the crucial role of the strain effect in determining the properties of the technologically important perovskite epitaxial thin films.

YBa2Cu3O7- delta -single crystals and epitaxial 123-films of different types (pulsed laser ablated, DC-magnetron sputtered and coevaporated by MBE) have been irradiated with fast neutrons (E>0.1MeV). After irradiation, the activation energy Ueff and the critical current density jc increase, especially at low temperatures (<40 K) and in small magnetic fields (<2T), whereas at higher temperatures and higher magnetic fields Ueff decreases after irradiation. The enhancement of Ueff is about a factor of up to 2 and seems not necessarily related to a simultaneous increase of jc. Jc increases in epitaxial thin films at 4.2 K by 300% in magnetic fields and by 50% in vanishing field. U*eff, which is obtained from rho (T)-measurements increases slightly after irradiation in a good agreement with the corresponding jc enhancement. The current-voltage characteristics E(j) shows after irradiation a strong reduction of flux flow in the high current regime.

Birefringence and electro-optic effect in epitaxial BST thin films

For progress in natural science: Materials international investigations of structural phase transformation and THz properties across metal–insulator transition in VO2/Al2O3 epitaxial films

Transverse and longitudinal magnetoresistances of p -type tellurium were investigated in the temperature range from 0.4 K to 4.2 K under magnetic field up to 18 kOe. The samples were not intentionally doped and their carrier concentrations were ranging form 1.9 to 6.6×10 14 cm -3 . The transverse magnetoresistances almost linearly depended on the magnetic field from 1.5 kOe to 18 kOe in contrast to the usual transverse magnetoresistance and they reached a large value of about 500% at 18 kOe around 0.4 K. The longitudinal magnetoresistances also showed linear magnetic field dependences and increased with decreasing temperature. They reached also a large value of about 400% at 18 kOe at 0.4 K. These could be interpreted consistently on the basis of the new kind of two-carrier model in which the impurity band-like states exist at 4.5 K(∼0.4 meV) below the top of the valence band and they shift upward relative to the top of the valence band in the magnetic field. The coefficient of the relative shift is estim...