We show, by SQUID magnetometry, that in (Ga,Mn)As films the in-plane uniaxial magnetic easy axis is consistently associated with particular crystallographic directions and that it can be rotated from the [-110] direction to the [110] direction by low temperature annealing. We show that this behavior is hole-density-dependent and does not originate from surface anisotropy. The presence of uniaxial anisotropy as well its dependence on the hole-concentration and temperature can be explained in terms of the p-d Zener model of the ferromagnetism assuming a small trigonal distortion.Comment: 4 pages, 6 Postscript figures, uses revtex

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We report on the observation of the Ising quantum Hall ferromagnet with Curie temperature T(C) as high as 2 K in a modulation-doped (Cd,Mn)Te heterostructure. In this system field-induced crossing of Landau levels occurs due to the giant spin-splitting effect. Magnetoresistance data, collected over a wide range of temperatures, magnetic fields, tilt angles, and electron densities, are discussed taking into account both Coulomb electron-electron interactions and s-d coupling to Mn spin fluctuations. The critical behavior of the resistance "spikes" at T-->T(C) corroborates theoretical suggestions that the ferromagnet is destroyed by domain excitations.

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The aim of the study was to determine the changes in the selected biochemical serum parameters in male Ross 308 broilers during the fattening period. The birds were kept under standard farm conditions and they were fed on commercial mixtures. The blood for analysis was taken from the jugular vein on the 14 th , 21 st , and 42 nd days of age. The concentration of serum protein (total protein, albumins, uric acid, creatinine), lipid (TG, TCHL, HDL) and mineral (Ca, P i , Mg, Fe) indices were determined. The measurements were carried out with the use of Epoll 20 photometer. The content of LDL and VLDL lipoprotein fractions was calculated on the basis of the Friedewald equation. Most of the estimated parameters, except for LDL and P i , were age-dependent (P<0.05). Total protein, albumins and total Ca levels showed a constant increase between the 14 th and 42 nd days of life. A lower (P<0.05) concentration of TG, TCHL, HDL, VLDL, Mg and Fe was determined at the end of the fattening period compared to 14-day-old broilers. A significant decrease of TG, VLDL, Mg and Fe content was noted already in the first age range (days 14-21) while in the case of TCHL and HDL a significant decrease was found between the 21 st and 42 nd days of fattening. The obtained results may be helpful in the evaluation of changes in the metabolic profile, health condition and production patterns in growing broiler chickens reared under farm conditions.

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