Intrinsic Structural Disorder and the Magnetic Ground State in Bulk EuTiO3

The magnetic properties of single-crystal EuTiO3 are suggestive of nanoscale disorder below its cubic-tetragonal phase transition. We demonstrate that electric field cooling acts to restore monocrystallinity, thus confirming that emergent structural disorder is an intrinsic low-temperature property of this material. Using torque magnetometry, we deduce that tetragonal EuTiO3 enters an easy-axis antiferromagnetic phase at 5.6 K, with a first-order transition to an easy-plane ground state below 3 K. Our data is reproduced by a 3D anisotropic Heisenberg spin model.Comment: 5 pages, 4 figure

Mass enhancement and magnetic order at the Mott-Hubbard transition

We study the evolution with pressure P and band filling y of the heat capacity, Hall coefficient, and resistivity at the approach to the T→0 Mott-Hubbard metal-insulator transition (MIT) in highly correlated V_(2-y)O_3. Under P, the electronic effective mass m* diverges at the MIT with a negligible change in carrier concentration n away from half-filling. Conversely, in the doped system m* actually decreases as the MIT is approached, while n increases linearly with y. The low-T magnetic order in the metal helps us deconvolute contributions from charge correlations and spin fluctuations

Effect of correlations and disorder on electron states in the Mott-Hubbard insulator V_2O_3

We compare vanadium-deficient (nonstoichiometric) and titanium-doped vanadium sesquioxide through measurements of the electrical resistivity at a series of hydrostatic pressures, the magnetic susceptibility, and the low-temperature specific heat: all as a function of T. The pressure dependence of the critical temperature for this discontinuous metal-antiferromagnetic-insulator transition as well as the temperature dependence of the magnetic susceptibility track in the two cases. However, the pressure dependence of the Hubbard gap, the slower than exponential form of the low-temperature resistivity, and the concentration of two-level systems are markedly different for V_(1.9967)O_3 and (V_(0.99)Ti_(0.01))_2O_3. We discuss our results in terms of the intra-atomic Coulomb repulsion, which is of comparable magnitude to the bare bandwidth of the vanadium 3d states. The band splitting in the antiferromagnetic insulating state is argued to cross over to a Slater-type splitting between the subbands narrowed by correlations with a sufficient degree of oxygen nonstoichiometry or Ti doping

Magnetic and transport studies of pure V_2O_3 under pressure

We report a systematic study of the resistivity and magnetic susceptibility of pure V_2O_3, the original Mott-Hubbard system at half filling, for pressures 0≤P≤25 kbar and temperatures 0.35≤T≤300 K. We also study (V_(0.99)Ti_(0.01)_2O_3 under pressure in order to elucidate the role of disorder on a metal-insulator transition in the highly correlated limit. Despite the low level of doping, we find that the two systems are very different. We observe a conventional collapsing of the Mott-Hubbard gap only for stoichiometric V_2_O3; the Ti disorder stabilizes the long-range antiferromagnetic order and a magnetic Slater gap. Moreover, we discover different P-T phase diagrams for the two systems, with a decoupling of the charge and spin degrees of freedom at the approach to the T=0, pressure-driven metal-insulator transition in pure V_2O_3

Verwey transition in Fe3_{3}O4_{4} at high pressure: quantum critical behavior at the onset of metallization

We provide evidence for the existence of a {\em quantum critical point} at the metallization of magnetite Fe$_{3}$O$_{4}$ at an applied pressure of $p_{c} \approx 8$ GPa. We show that the present ac magnetic susceptibility data support earlier resistivity data. The Verwey temperature scales with pressure $T_{V}\sim (1-p/p_{c})^{\nu}$, with $\nu\sim 1/3$. The resistivity data shows a temperature dependence $\rho(T)=\rho_{0}+AT^{n}$, with $n\simeq 3$ above and 2.5 at the critical pressure, respectively. This difference in $n$ with pressure is a sign of critical behavior at $p_{c}$. The magnetic susceptibility is smooth near the critical pressure, both at the Verwey transition and near the ferroelectric anomaly. A comparison with the critical behavior observed in the Mott-Hubbard and related systems is made.Comment: 5 pages, 5 figure

Magnetoelastic relaxations in EuTiO3

The multiferroic properties of EuTiO3 are greatly enhanced when a sample is strained, signifying that coupling between strain and structural, magnetic or ferroelectric order parameters is extremely important. Here resonant ultrasound spectroscopy has been used to investigate strain coupling effects, as well as possible additional phase transitions, through their influence on elastic and anelastic relaxations that occur as a function of temperature between 2 and 300 K and with applied magnetic field up to 14 T. Antiferromagnetic ordering is accompanied by acoustic loss and softening, and a weak magnetoelastic effect is also associated with the change in magnetization direction below . Changes in loss due to the influence of magnetic field suggest the existence of magnetic defects which couple with strain and may play a role in pinning of ferroelastic twin walls

New perspectives for eye-sparing treatment strategies in primary uveal melanoma

Uveal melanoma is the most common intraocular malignancy and arises from melanocytes in the choroid, ciliary body, or iris. The current eye-sparing treatment options include surgical treatment, plaque brachytherapy, proton beam radiotherapy, stereotactic photon radiotherapy, or photodynamic therapy. However, the efficacy of these methods is still unsatisfactory. This article reviews several possible new treatment options and their potential advantages in treating localized uveal melanoma. These methods may be based on the physical destruction of the cancerous cells by applying ultrasounds. Two examples of such an approach are High-Intensity Focused Ultrasound (HIFU)—a promising technology of thermal destruction of solid tumors located deep under the skin and sonodynamic therapy (SDT) that induces reactive oxygen species. Another approach may be based on improving the penetration of anti-cancer agents into UM cells. The most promising technologies from this group are based on enhancing drug delivery by applying electric current. One such approach is called transcorneal iontophoresis and has already been shown to increase the local concentration of several different therapeutics. Another technique, electrically enhanced chemotherapy, may promote drug delivery from the intercellular space to cells. Finally, new advanced nanoparticles are developed to combine diagnostic imaging and therapy (i.e., theranostics). However, development. these methods More are mostly advanced at an and early targeted stage of preclinical development. studies More and advanced clinical trials and targeted would be preclinical needed to studies introduce and some clinical of trials these would techniques be needed to routine to introduce clinical practice. some of these techniques to routine clinical practice

Aspects of finite electrodynamics in D=3 dimensions

We study the impact of a minimal length on physical observables for a three-dimensional axionic electrodynamics. Our calculation is done within the framework of the gauge-invariant, but path-dependent, variables formalism which is alternative to the Wilson loop approach. Our result shows that the interaction energy contains a regularised Bessel function and a linear confining potential. This calculation involves no theta expansion at all. Once again, the present analysis displays the key role played by the new quantum of length.Comment: 12 pages, 2 figures; reference list updated and extended; new aknowlegments; removed line after eq.(1) erroneously inserte