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Properties of fragmentation from an explosively driven 316L stainless steel spherical shell section fabricated by a laser powder bed additive manufacturing process with minimal surface finishing are investigated. This shell is driven by an insensitive high explosive, resulting in high strain rate deformation (>8 × 103 s−1) and failure of the stainless steel. Photonic Doppler velocimetry measures the expansion rate; dynamic radiography and high-speed imaging capture the fracture behavior of the stainless steel. The fracture response of the additively manufactured stainless steel shell is compared to published experimental results on additively manufactured 316L stainless steel and conventionally manufactured wrought 316L and 304 stainless steel shell fragmentation. Despite preferred crack orientation, suggesting the influence of surface grooves on fracture time, fragment size is identical to that measured in a similar experiment on wrought 304 stainless steel. Further analysis indicates that the 316L additively manufactured stainless steel shell exhibits comparable spall strength and fragmentation toughness to conventionally manufactured stainless steel yet lower failure strain due to surface stress concentrations. [ABSTRACT FROM AUTHOR]

The double-wave method is widely used in ferroelectric measurements to eliminate the effects of conductance and capacitance components while preserving the ferroelectric domain contribution. However, in polycrystalline ferroelectric material, the assumption of the evolution of domains by the double-wave method no longer applies due to the domain back switch of de-field, and the domain contribution calculated by the current subtraction method is also problematic. Therefore, we proposed a new method to calculate the charge contribution of conductance and eliminate the conductance interference in the hysteresis loop. Finally, the feasibility of this new method is verified in many typical polycrystalline ferroelectric materials. This work provides a path for the study of ferroelectric properties of some high conductivity materials. [ABSTRACT FROM AUTHOR]

Hexagonal yttrium manganite (YMnO3) and chromium doped yttrium manganite (YMn1 – xCrxO3) were prepared by the solid-state method. X-ray diffraction and Raman scattering were combined to explore the structural characterization. Structural analysis illustrates that the lattice is compressed and the tilt of the MO5 (M = Cr or Mn) bipyramid is decreased with an increase in Cr3+ concentration, leading to declining frustration. Magnetic measurement suggests both weak ferromagnetic (FM) and antiferromagnetic (AFM) orderings enhanced with the growth of doping concentration. Enhanced weak FM ordering may arise from breaking of the superexchange interaction and introduction of the double-exchange interaction inside the layers, and the increased AFM ordering is attributed to the improved coupling between neighboring planes that resulted from the structural distortion. Spin-phonon coupling is discussed to confirm the enhanced coupling between interplane Mn3+ moments. [ABSTRACT FROM AUTHOR]

Laser-induced femtosecond demagnetization, femtomagnetism, offers a potential route to develop faster magnetic storage devices. It is generally believed that the traditional spin-wave theory, which is developed for thermally driven slow demagnetization, cannot explain this rapid demagnetization by design. Here, we show that this traditional spin-wave theory, once augmented by laser-induced spin–orbit torque, provides a highly efficient paradigm for demagnetization, by capturing low-energy spin-wave excitation that is absent in existing mechanisms. Our paradigm is different from existing ones but does not exclude them. Microscopically, we find that optical spin–orbit torque generates massive spin waves across several hundred lattice sites, collapsing the long-range spin-spin correlation within 20 fs. Our finding does not only explain new experiments but also establishes an alternative paradigm for femtomagnetism. It is expected to have far-reaching impacts on future research. [ABSTRACT FROM AUTHOR]

A series of polycrystalline YMn1-xRuxO3 (0≤x≤0.2) samples were prepared by traditional solidstate reaction method. Effects of doping on the microstructures and magnetic properties were investigated. Microstructural results reveal that samples crystallize in a single hexagonal structure with P63cm group for x≤0.1. Lattice parameters a, c, and unit-cell volume of YMn1-xRuxO3 are found to increase with doping content, which are ascribed to the larger radius of Ru3+ than that of Mn3+. Weak ferromagnetism is found and is enhanced with increasing doping concentration x. The bond angles of Mn-O3-Mn and Mn-O4-Mn are changed in the opposite trends, which break the Mn-Mn exchange interaction, thus the antiferromagnetic ordering. The MnO5 bipyramid is found to be relieved and the trimerization of Mn ions is weakened. These structural modifications result in the increase of weak ferromagnetism ordering in samples. [ABSTRACT FROM AUTHOR]

The structural, electronic, and magnetic properties of (La2/3Sr1/3MnO3)m/(SrRuO3)n superlattices have been investigated based on the first principles calculations. An obvious Jahn-Teller distortion, which depends on m, n, appears in MnO6 octahedron in the superlattices. The stretch along c-axis of MnO6 octahedron at the interface lifts the Mn eg orbital degeneracy, with electrons preferring the lower energy 3z2 - r2 to the higher energy x2 - y2. Benefitting from the charge transfer at the interface, the still occupied x2 - y2 orbital can mediate a robust in-plane double exchange interaction. La2/3Sr1/3MnO3 block is ferromagnetic and metallic, even for the superlattice with m=n=1. [ABSTRACT FROM AUTHOR]

LaMnO3+δ films with various thicknesses were grown on LaAlO3 (001) single crystal substrate to investigate the effect of in-plane compressive strain (~-0.57%) on magnetic properties. All films exhibit a blocking temperature Tb at which the zero field cooled magnetization reaches a maximum, indicating the ferromagnetic (FM) nanoclusters are embedded in the background of antiferromagnetic (AFM) matrix. The onset temperature of FM transition Tc and Tb is increased by 24% and 89%, respectively, with the thickness decreasing from 82.4 nm to 9.2 nm. Simultaneously, the saturation magnetization greatly increases by 309%, which is ascribed to the strain-induced transition of AFM to FM phase due to the orbital order structure switching from x²- 1/y²-1 [A-type] to (x²- y²) + (z²- 1) [F-type]. [ABSTRACT FROM AUTHOR]