A magnetic refrigeration apparatus (10) is modular in design, so that housing modules (14) are alternately stacked with superconducting magnet pairs (24). Each module (14) has a wheel (16) that is rotated through the module (14), the wheel (16) having cutout regions (18) into which elements (20) of magnetic material are inserted. Each cutout region has two elements (20) separated by a wave spring, the wave spring biasing the elements (20) against the housing module (14) so that the elements (14) are in slidable contact with the module (14) upon rotation. In operation, the wheel (16) carries the elements (20) cyclically between high and low magnetic field zones. In low field regions the elements (20) are cooled by the magnetocaloric effect and heat exchangers absorb heat from either a stagnant subcooled superfluid helium bath or a forced-flow subcooled superfluid helium stream. In high field regions the elements (20) are heated by the magnetocaloric effect and a force-flow stream of liquid helium passes through the high temperature heat exchangers absorbing heat from the magnetic refrigeration apparatus (10).
c-axis oriented microwave quality HTSC films are deposited onto single crystals of gadolinium gallium garnet (GGG) using pulsed laser deposition (PLD) with conditions of 85 mTorr of oxygen partial pressure, a block temperature of 730.degree. C., a substrate surface temperature of 790.degree. C. and a laser fluence of 1 to 2 Joules/cm.sub.2 at the target, a laser repetition rate of 10 Hz and a target to substrate distance of 7 cm and in which the a and b lattice parameters of the GGG exhibit a mismatch of less than 2.5 percent with the a and b lattice parameters of the HTSC.
A refrigerator for cooling a sample (16,17) comprising a reservoir (1) for storing gaseous .sup.4 He when in use; a cooler (13) for cooling gaseous .sup.4 He from the reservoir; and a helium vessel (18,19) for containing .sup.4 He, the .sup.4 He in the helium vessel being in fluid communication with the reservoir (1) via the cooler (13). The sample (16,17) is mounted, in use, in thermal contact with the .sup.4 He in the helium vessel whereby the .sup.4 He in the helium vessel provides a path for heat to transfer from the sample to the cooler.
c-axis oriented high temperature superconductors are deposited onto new compositions of garnets using pulsed laser deposition (PLD) with conditions of 85 mTorr of oxygen partial pressure; a block temperature of 730.degree. C., a substrate surface temperature of 790.degree. C. and a laser fluence of 1 to 2 Joules/cm.sup.2 at the target, a laser repetition rate of 10 Hz and a target to substrate distance of 7 cm and in which the a and b lattice parameters of the new compositions of garnets exhibit a mismatch of less than 7 percent with the a and b lattice parameters of the HTSC.
A magnetic heating and cooling system is disclosed. A magnetic fluid is pumped through at least a portion of the heating and cooling system. The fluid moves through the field of a superconducting or other type of magnet. When the fluid enters the magnetic field, it is heated as a result of the magnetization. Heat from the magnetic fluid is then transferred to a regenerator chamber. When the fluid leaves the magnetic field it is chilled. Heat from a regenerator chamber is then transferred to the fluid. External loads or sinks are heated or cooled.
A magnetic process comprising: subjecting a magnetically susceptible media to a magnetic field wherein the fluid is magnetized and the magnetized media absorbs the heat of magnetization; transferring the absorbed heat from the magnetized fluid or solid to a heat sink; removing the magnetized magnetic media from the magnetic field, wherein the magnetic media undergoes spontaneous cooling to produce a cooled magnetic media; and providing heat to the cooled magnetic media from a heat source, and wherein said process is accomplished at above about 275 degrees Kelvin.
