We present a parametric study of the diffuse magnetic scattering at $(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ positions in reciprocal space, ascribed to a frozen antiferromagnetic spin ice state in single-crystalline ${\mathrm{Tb}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$. Our high-resolution neutron scattering measurements show that the elastic $(-0.02$ meV $<E<0.02$ meV) $(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ scattering develops strongly below $\approx$275 mK, and correlates with the opening of a spin gap of $\approx 0.06$ to 0.08 meV over most of the Brillouin zone. The nature of the transition at 275 mK has many characteristics of spin glass behavior, consistent with ac-susceptibility measurements. The application of a magnetic field of 0.075 T applied along the $\left[1\overline{1}0\right]$ direction destroys the $(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ elastic scattering, revealing the fragility of this short-range ordered ground state. We construct a refined $H$-$T$ phase diagram for ${\mathrm{Tb}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ and $\left[1\overline{1}0\right]$ fields which incorporates this frozen spin ice regime and the antiferromagnetic long-range order previously known to be induced in relatively large fields. Specific heat measurements on the same crystal reveal a sharp anomaly at $T_{\mathrm{c}}\approx$ 450 mK and no indication of a transition near $\approx$275 mK. We conclude that the higher temperature specific heat peak is not related to the magnetic ordering but is likely a signal of other, nonmagnetic dipole correlations.

Biological bioprostheses such as grafts, patches, and heart valves are often derived from biological tissue like the pericardium. These bioprostheses can be of xenogenic, allogeneic, or autologous origin. Irrespective of their origin, all types are pre-treated via crosslinking to render the tissue non-antigenic and mechanically strong or to minimize degradation. The most widely used crosslinking agent is glutaraldehyde. However, glutaraldehyde-treated tissue is prone to calcification, inflammatory degradation, and mechanical injury, and it is incapable of matrix regeneration, leading to structural degeneration over time. In this work, we are investigating an alternative crosslinking method for an intraoperative application. The treated tissue‘s crosslinking degree was evaluated by differential scanning calorimetry. To confirm the findings, a collagenase assay was conducted. Uniaxial tensile testing was used to assess the tissue’s mechanical properties. To support the findings, the treated tissue was visualized using two-photon microscopy. Additionally, fourier transform infrared spectroscopy was performed to study the overall protein secondary structure. Finally, a crosslinking procedure was identified for intraoperative processing. The samples showed a significant increase in thermal and enzymatic stability after treatment compared to the control, with a difference of up to 22.2 °C and 100%, respectively. Also, the tissue showed similar biomechanics to glutaraldehyde-treated tissue, showing greater extensibility, a higher failure strain, and a lower ultimate tensile strength than the control. The significant difference in the structure band ratio after treatment is proof of the introduction of additional crosslinks compared to the untreated control with regard to differences in the amide-I region. The microscopic images support these findings, showing an alteration of the fiber orientation after treatment. For collagen-based biomaterials, such as pericardial tissue, the novel phenolic crosslinking agent proved to be an equivalent alternative to glutaraldehyde regarding tissue characteristics. Although long-term studies must be performed to investigate superiority in terms of longevity and calcification, our novel crosslinking agent can be applied in concentrations of 1.5% or 2.0% for the treatment of biomaterials.

The work establishes a connection between the thermodynamics and crystal growth of Bi₂M²⁺O₄ and reveals new insights into the description and understanding of the growth process and its optimization.

We present a study of the control of electric field induced strain on the magnetic and electrical transport properties in a magnetoelastically coupled artificial multiferroic ${\mathrm{Fe}}_3{\mathrm{O}}_4/{\mathrm{BaTiO}}_3$ heterostructure. In this ${\mathrm{Fe}}_3{\mathrm{O}}_4/{\mathrm{BaTiO}}_3$ heterostructure, the ${\mathrm{Fe}}_3{\mathrm{O}}_4$ thin film is epitaxially grown in the form of bilateral domains, analogous to a-c stripe domains of the underlying ${\mathrm{BaTiO}}_3\left(001\right)$ substrate. By in situ electric field dependent magnetization measurements, we demonstrate the extrinsic control of the magnetic anisotropy and the characteristic Verwey metal-insulator transition of the epitaxial ${\mathrm{Fe}}_3{\mathrm{O}}_4$ thin film in a wide temperature range between 20–300 K, via strain mediated converse magnetoelectric coupling. In addition, we observe strain induced modulations in the magnetic and electrical transport properties of the ${\mathrm{Fe}}_3{\mathrm{O}}_4$ thin film across the thermally driven intrinsic ferroelectric and structural phase transitions of the ${\mathrm{BaTiO}}_3$ substrate. In situ electric field dependent Raman measurements reveal that the electric field does not significantly modify the antiphase boundary defects in the ${\mathrm{Fe}}_3{\mathrm{O}}_4$ thin film once it is thermodynamically stable after deposition and that the modification of the magnetic properties is mainly caused by strain induced lattice distortions and magnetic anisotropy. These results provide a framework to realize electrical control of the magnetization in a classical highly correlated transition metal oxide.