NOVEL SPINTRONIC MATERIALS BASED ON FERROMAGNETIC SEMICONDUCTOR CHALCOPYRITES

Ternary diamond-like compounds in II–IV–V2 semiconductor system heavily-doped with transition d-element Mn have been recently prepared. The materials grown in both forms — single crystal layers and polycrystalline bulks — exhibit well defined ferromagnetic hysteresis with a saturation behavior in the magnetization curve up to above room temperature. Curie temperatures are of TC=310 K to 320 K for ( Cd 1-x Mn x) GeP 2 and ( Zn 1-x Mn x) GeP 2 compounds. The chemical states in the bulk of ZnGeP 2: Mn and interface of Mn -doped ferromagnetic layer on ZnGeP 2 (001) crystal, have been clarified by electron paramagnetic resonance and in situ photoemission spectroscopy. The as-prepared surface consists of Ge -rich, metallic Mn -compound. In and below the sub-surface region, dilute Mn 2+ species as precursors of the DMS phase exist. Mn 2+ ions are paramagnetic active on Zn 2+ sites in the bulk and show five EPR sets of equidistant peaks. Theoretical band-gap calculation suggests a predominant antiferromagnetic order in stoichiometric ( Cd , Mn ) GeP 2 but the systems with vacancies as ( Cd , V C , Mn ) GeP 2 or ( Cd , Ge , Mn ) GeP 2 are ferromagnetic and energetically stable. These materials are of great promise for room-temperature spintronics applications.

White blood cell counts in bursectomized birds

Birds were bursectomized before 3 days of age. Bursectomy did not significantly influence the total or absolute number of leukocytes at 12, 19, or 41 days of age. The bursectomized birds contained significantly fewer small lymphocytes at 5 and 41 days of age than medium lymphocytes. A single intravenous injection of 4 IU or 6 USP units of ACTH/100 g body weight significantly increased the absolute heterophil counts of both sham and bursectomized birds. However, only the bursectomized birds showed a significant decline in the absolute count of lymphocytes. The results suggest that the bursa of Fabricius is necessary for an optimum level of circulating lymphocytes. The bursa may influence the lymphocyte count by releasing specific cells or elaborating a humoral factor.

Effect of ACTH on total adrenal cholesterol in bursectomized chicks

The effect of ACTH on the level of total adrenal cholesterol was studied in chemically or surgically bursectomized chicks. Total adrenal cholesterol was determined 12–15 hr after a single injection of 1 or 3 USP units of ACTH to 21-, 46-, and 60-day-old chicks. The adrenal cholesterol of control (12.9–16.7 µg/mg adrenal), surgically bursectomized (14.6– 18.2 µg/mg), and chemically bursectomized (13.3–14.2 µg/ mg) chicks receiving an injection of 3 USP units of ACTH was significantly lower than the cholesterol level (22.0–28.5 µg/ mg) of similar chicks not receiving ACTH. The results obtained from three trials suggest that the bursa of Fabricius does not influence the level of cholesterol in the adrenal gland. Also, it was found that ACTH will reduce the adrenal cholesterol of young birds.