We have recently observed a giant electrocaloric effect (12 K in 25 V) in 350 nm sol-gel Pb Zr_0.95 Ti_0.05 O_3 films near the ferroelectric Curie temperature of 242oC. Here we demonstrate a giant electrocaloric effect (5 K in 25 V) in 260 nm sol-gel films of the relaxor ferroelectric 0.9 PbMg_(1/3)Nb_(2/3)O_3 - 0.1 PbTiO_3 near the Curie temperature of 60oC. This reduction in operating temperature widens the potential for applications in novel cooling systems.

The authors have recently observed a giant electrocaloric effect (12K in 25V) in 350nm sol-gel PbZr0.95Ti0.05O3 films near the ferroelectric Curie temperature of 242°C. Here the authors demonstrate a giant electrocaloric effect (5K in 25V) in 260nm sol-gel films of the relaxor ferroelectric 0.9PbMg1∕3Nb2∕3O3–0.1PbTiO3 near the Curie temperature of 60°C. This reduction in operating temperature widens the potential for applications in cooling systems.

A Co valence tautomeric compound has been studied in a wide range of magnetic fields and temperatures. Magnetic susceptibility of the Co complex has been measured in explosive magnetic fields. An anomalous behaviour of the susceptibility curve at the field of 100T was attributed to a field-induced phase transition. A model describing the phase transition was developed. Among the results of the model is a B–T phase diagram of the transition, where B is magnetic field and T is temperature. The obtained experimental results were analyzed in the framework of the proposed model and several important parameters have been estimated: value of the entropy change at the transition and energy difference between the two phases.

An applied electric field can reversibly change the temperature of an electrocaloric material under adiabatic conditions, and the effect is strongest near phase transitions. We demonstrate a giant electrocaloric effect (0.48 kelvin per volt) in 350-nanometer PbZr0.95Ti0.05O3 films near the ferroelectric Curie temperature of 222°C. A large electrocaloric effect may find application in electrical refrigeration.

New approaches to thermal management of electronic components are of general interest. Our work demonstrates a novel solution for this applications area. Highly effective thermal management solutions can potentially help the semiconductor manufacturers to reduce costs and meet some milestones of the silicon roadmap. For example, enormous amount of Joule heating and inability of the state-of-the art coolers to cope with it forces manufacturers to switch to dual-core architectures of processors. Also, our work might inspire a number of blue skies research projects in this particular field because it points to a relatively new approach broadens the scope of applications for ferroelectrics. We have observed large cooling (electrocaloric) effects in thin films under the application of a small electrical voltage. This effect could also be used in reverse to turn low grade waste heat into electricity (pyroelectric energy conversion). In other words, we suggest a way to interconvert thermal end electrical energy

Field-induced α–γ phase transition in metallic Ce is studied in the framework of the Anderson impurity Hamiltonian with the account of the Falicov–Kimball interaction. No fitting parameters are used. Both zero and finite temperature cases are considered and yield a number of important characteristics: B–T phase diagram, where B is magnetic field and T is temperature, the critical magnetic field value of the transition at zero temperature (BC=160T), magnetization versus magnetic field and temperature dependencies in the vicinity of the transition, value of the magnetization jump at different temperatures, etc. The obtained magnetization jump is enough to be detected by a modern megagauss explosion technique.

Ultrahigh magnetic fields (B = 100-1000 T) are valuable means for many-sided research in solid state physics. A brief description of the explosion method and some results of its application are presented. The magnetic coil compensation method has been used to study the first order phase transitions in a broad range of fields and temperatures. The Faraday rotation method has been applied to measure the second order magnetic phase transitions. A number of magnetic materials were studied experimentally and theoretically: first order phase transitions in RCo2 compounds, second order transitions in KMnF3, MnF2, etc. and steplike quantum magnetization process (transition from ferrimagnetic to ferromagnetic phase) in some mesoscopic magnets - Mn12Ac, Mn(6)Rad(6) and V-15. These magnetic measurements provide us with a direct and unique method of determination of the exchange interactions between magnetic ions in magnetic moleculas. The knowledge of the magnetic interacion energies is important for molecular engineering in order to design new magnetic nanoscale materials with desireable properties. The intramolecule exchange integrals of the magnetic nanoclusters Mn12Ac, Mn(6)Rad(6) and V-15 that have been determined by this method are presented.

The multipole expansion technique is applied to one of the largest magnetic molecules, Fe-30. The molecule's dipole, toroid and quadrupole magnetic moments are equal to zero (in the absence of magnetic field) so the multipole expansion starts from the octopole moment. Probably, the Fe30 molecule is the most symmetrical magnetic body synthesized so far. The magnetization process is considered theoretically in different geometries. Some components of the octopole moment experience a jump while the magnetization rises linearly up to its saturation value. An elementary octopole moment consisting of four magnetic dipoles is proposed as a hint for designing of an experiment for the measurement of octopole magnetic-moment components.

A new construction of the spin transistor is proposed and its volt–ampere characteristics (VAC) are theoretically investigated. It is based on the ferromagnetic half-metals and is referred to as a spin half-metallic transistor (SHMT). SHMT is revealed to amplify electric current as a bipolar transistor. At the same time, its properties drastically depend on the reciprocal orientation of magnetizations of its three junctions; so SHMT can be used as a switching device. Also properties of an “F↑–F↓ junction” are considered. This device consists of two half-metallic electrodes with antiparallel magnetizations. Its VAC reminds VAC of a diode in some voltage range. Behavior of the F↑–F↓ junction under different conditions is considered.

Magnetic properties of the Co valence tautomers are considered in wide range of magnetic field and temperature. Particularly, a model of the first order structural phase transition accompanied by a magnetic moment jump is proposed. The phase diagrams of the phase transition on a B-T plane (B is magnetic field and T is temperature) are calculated for four ligand types. Dependence of the critical magnetic field on physical characteristics known from experiments (transition temperature at the absense of magnetic field, entropy change per formula unit, energy difference between two phases) is found. The phase diagram is parametrized for comparison with other phase transitions of this kind.

A wide class of magnetic molecular materials - molecular clusters with high magnetic moment containing 3d transition metals (such as `Fe8', `Mn12ac', etc) - have been considered from the point of view of their use as refrigerants in low-temperature regions. The consideration was made in the framework of the model based on the Langevin theory of a superparamagnet. The magnetic entropy change caused by a change in an external magnetic field was calculated for various magnetic clusters. The estimations made show that the magnetic molecular clusters could be promising materials for magnetic refrigeration in low-temperature regions (below about 20 K).