Nb+Al) codoped rutile TiO 2 ceramics with nominal composition Ti 4+ 0.995 Nb 5+ 0.005y Al 3+ 0.005z O 2 , z = (4−5y)/3 and y = 0.4, 0.5, 0.6, 0.7, and Ti 4+ 0.90 Nb 5+ 0.05 Al 3+ 0.05 O 2 have been synthesized. The resultant samples in ceramic pellet form exhibit a colossal dielectric permittivity (>∼10 4 ) with an acceptably low dielectric loss (∼10 −1 ) after optimization of the processing conditions. It is found that a conventional surface barrier layer capacitor (SBLC) effect, while it contributes significantly to the observed colossal permittivity, is not the dominant effect. Rather, there exists a subtle chemical compositional gradient inward from the pellet surface, involving the concentration of Ti 3+ cations gradually increasing from zero at the surface without the introduction of any charge compensating oxygen vacancies. Instead, well-defined G r ± 1 / 3 [011]* satellite reflections with the modulation wave-vector q = 1 / 3 [011] r * and sharp diffuse streaking running along the G r ± ε[011]* direction from electron diffraction suggest that the induced additional metal ions appear to be digested by a locally intergrown, intermediate, metal ion rich structure. This gradient in local chemical composition exists on a scale up to ∼ submillimeters, significantly affecting the overall dielectric properties. This work suggests that such a controllable surface compositional gradient is an alternative method to tailor the desired dielectric performance.

No abstract

We present the results of electrically-detected magnetic resonance (EDMR) experiments on ion-implanted Si:P nanostructures at 5 K, consisting of high-dose implanted metallic leads with a square gap, in which Phosphorus is implanted at a non-metallic dose corresponding to 10 17 cm −3 . By restricting this secondary implant to a 100 nm × 100 nm region, the EDMR signal from less than 100 donors is detected. This technique provides a pathway to the study of single donor spins in semiconductors, which is relevant to a number of proposals for quantum information processing. The ability to spectroscopically study the spin properties and interactions of a small number of donors in semiconductors has many applications such as the storage of classical information in nuclear or electronic spins, 1 and is relevant to a number of proposals 2,3 related to quantum information processing (QIP). In particular, the construction of QIP hardware utilizing Si:P has been discussed by Kane 4 and Hollenberg. 5 In this context, the ultimate task is the detection of the electron or nuclear spin state of single P donors.

No abstract

The magnetic properties and magnetocaloric effect (MCE) in the ternary intermetallic compound ErMn2Si2 have been studied by magnetization and heat capacity measurements. A giant reversible MCE has been observed, accompanied by a second order magnetic phase transition from paramagnetic to ferromagnetic at ∼4.5 K. Under a field change of 5 T, the maximum value of magnetic entropy change (−ΔSMmax) is 25.2 J kg−1 K−1 with no thermal and field hysteresis loss, and the corresponding maximum value of adiabatic temperature change (ΔTadmax) is 12.9 K. Particularly, the values of −ΔSMmax and ΔTadmax reached 20.0 J kg−1 K−1 and 5.4 K for a low field change of 2 T, respectively. The present results indicate that the ErMn2Si2 compound is an attractive candidate for low temperature magnetic refrigeration.

This work explores the magnetic properties of Fe 0.5 Ni 0.5 PS 3 . The system shows pronounced hysteresis in the magnetic phase transition temperature as a function of the direction of the change in temperature. Field cooled/zero field cooled hysteresis is not pronounced. However, the transition temperature between antiferromagnetic and paramagnetic order occurs at approximately 97 K on cooling, but at 138 K on warming, whether the warming is after zero field or field cooling. This is indicative of magnetic glassiness, and made all the more unusual because all measurements exhibit a transition to a third magnetic phase existing at temperatures below $ 14 K. The intermediate phase relaxes on a laboratory time scale of the order of 48 min, into an antiferromagnetic state whose magnetic structure is, from neutron diffraction, indistinguishable from the low temperature state. This low temperature state shows magnetic ordering consistent with that observed in CoPS 3 and NiPS 3 . Analysis of the neutron measurements shows that the direction of moments cannot be along the b-axis. It is also shown that the moments are unlikely to lie in the c n direction. Therefore, we suggest that the moments lie along the a-axis.

No abstract

Selective formation of only one iron oxide phase is a major challenge in conventional laser ablation process, as is scaling up the process. Herein, superparamagnetic single-phase magnetite nanoparticles of hexagonal and spheroidal-shape, with an average size of ca. 15 nm, are generated by laser ablation of bulk iron metal at 1064 nm in a vortex fluidic device (VFD). This is a one-step continuous flow process, in air at ambient pressure, with in situ uptake of the nanoparticles in the dynamic thin film of water in the VFD. The process minimizes the generation of waste by avoiding the need for any chemicals or surfactants and avoids time-consuming purification steps in reducing any negative impact of the processing on the environment.