We report improvements in the crystallinity of a III-V-based diluted magnetic semiconductor (Ga,Mn)As by heat treatment (annealing) after growth at comparatively low temperatures. This method can be used to raise the Curie temperature to 100K without the need for severe optimization of growth conditions, as well as to adjust the material parameters to desired values.

This paper presents an axiomatic model of decision making under uncertainty which incorporates objective but imprecise information. Information is assumed to take the form of a probability-possibility set, that is, a set P of probability measures on the state space. The decision maker is told that the true probability law lies in P and is assumed to rank pairs of the form (P, f ) where f is an act mapping states into outcomes. The representation result delivers maxmin expected utility at each probability-possibility set. The model explains how "beliefs" vary with information:there is a mapping that gives for each probability-possibility set the revealed set of probability distributions. This allows both expected utility when the set is reduced to a singleton and extreme pessimism when the decision maker takes the worst case scenario in the entire probability-possibility set. We define a notion of comparative imprecision aversion and show it is characterized by inclusion of the sets of revealed probability distributions, irrespective of the utility functions that capture risk attitude. We also identify an explicit attitude toward imprecision that underlies usual hedging axioms. Finally, we characterize, under extra axioms, a more precise functional form, in which the set of revealed probability distributions is obtained by (i) solving for the "mean value" of the probability-possibility set, and (ii) shrinking the probability-possibility set toward the mean value to a degree determined by preferences.

Magnetic circular dichroism (MCD) of a ferromagnetic diluted magnetic semiconductor Ga1−xMnxAs films was measured to clarify their electronic structure. Strong enhancement of MCD by Mn substitution indicated a strong sp–d hybridization. The p–d exchange interaction was concluded to be antiferromagnetic, which was in contrast with the reported ferromagnetic p–d exchange in very diluted paramagnetic GaAs:Mn bulk crystals. The change of the character of the p–d exchange interaction is due to the unique feature of Ga1−xMnxAs that the relative abundance of the neutral and ionized Mn acceptors controls the p–d exchange.

Monosized spherical particles of (Zr,Sn)Ti04 with an average diameter of about 0.3 pm were synthesized by the controlled hydrolysis of metal alkoxides. The as-prepared, amorphous, particles were compacted without any sintering aid, crystallized, and then sintered at 1600°C for 3 h into bodies with >96.0% of theoretical density. The dense sintered bodies of (Zro.80Sno.zo)Ti04 showed good microwave characteristics: E~ = 40.0, Q = 5000, and 71 = 3 ppm/"C at 10 GHz. The dielectric constant was remarkably dependent upon the relative densities of the sintered bodies and the change of the lattice parameters, while Q value was mainly affected by the oxygen deficiency. An increase of the dielectric constant with the substitution of Sn4+ in ZrTi04 was attributable to the enhancement of ionic polarization with the increase of the c-axis length. [