F. T. Hedgcock

Bio: F. T. Hedgcock is an academic researcher. The author has contributed to research in topics: Crystal field theory & Magnetic susceptibility. The author has an hindex of 1, co-authored 2 publications receiving 8 citations.

Magnetic Anisotropy in Single Crystals of Zn–Mn and Zn–Cr

Abstract: We have extended the low temperature magnetic anisotropy measurements on single crystals of zinc containing up to 600 p.p.m. manganese from magnetic fields of 9 to 56 kG. The crystal field splitting parameters determined at low magnetic fields also characterizes the magnetic anisotropy at high magnetic fields. Manganese–manganese interaction effects are observed in the magnetic anisotropy at manganese concentrations greater than 300 p.p.m. Low temperature magnetic anisotropy measurements on single crystals of zinc containing up to 164 p.p.m. chromium are reported and indicate a crystal field splitting of 0.16 K for the chromium ion.

Influence of crystal field splitting of Mn and Cr on the electrical resistivity of zinc

Abstract: Investigations of the magnetic susceptibility indicate a possible crystal field splitting for both Mn and Cr in zinc with the Cr ground state supporting spin‐flip scattering whereas in the Mn ground state would not. Calculations indicate a qualitative difference in the low temperature electrical resistivity depending on whether the Kondo temperature is greater or smaller than the crystal field splitting. Measurements of the electrical resistivity of extremely dilute (<10 p.p.m.) zinc alloys containing manganese or chromium measured in the milli degree temperature range do not exhibit the detailed resistivity structure at least within the accuracy of 1 part in 104. However, below 0.1°K the resistivity does show the expected T2 law.

Kondo effect and impurity interactions in the resistivity of diluteZnMn alloys

Abstract: The electrical resistivity of diluteZnMn alloys (c=1.7–2400 ppm Mn) has been investigated in the temperature range from 0.05 to 14 K. For the most dilute sample, single-impurity Kondo behavior is found, well described by the Hamann formula withT K=0.9 K,S=3/2. ForT<50 mK, aT 2 law with θ R =0.3 K is expected. In the dilute limit the Kondo slope is −(1/c)d(Δρ)/d(logT)=3.7±0.2 µΩ-cm/at % dec. In the more highly concentrated alloys, the slope decreases with increasing c and the lnT-like variation of the Kondo resistivity roughly terminates near a temperatureT W(c),T W being related to the average Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction strength between the Mn impurities. For 20 ppm ≤c ≤ 1000 ppm, the resistivity slightly decreases at low temperatures and a broad resistivity maximum is observed atT m (c), withT m ∝c 0.7. ForT 2

Energy splittings of transition metal ions in non‐cubic hosts

Abstract: A number of recent experiments have shown evidence for energy splittings of paramagnetic ions in metallic hosts. Although theoretical attempts have been made to calculate so called ’’crystal field effects’’ in metals from first principles very little qualitative progress has been made on this very difficult subject. In this paper we wish to present a short summary of experimental results on the energy splittings of the manganese ion in h.c.p. hosts: Mg, Zn and Cd and also the energy splittings of two species of transition metal ions Mn and Cr in the same host‐metal, zinc. This summary of results will be compared with the recent theoretical work of Smith who considers spin‐orbit effects in metals. At least semi‐qualitative agreement is found in that the observed energy splittings scale with the spin‐orbit parameter of the host and the magnitude of the local moment‐conduction electron exchange interaction strength.

Magnetic anisotropy in dilute ZnMn single crystals at low temperatures

Abstract: The dc magnetization of ZnMn single crystals containing 34 and 62 ppm Mn has been measured between 0.015 and 50 K. The temperature dependence of the magnetization is shown to be strongly dependent on crystal orientation. Below 2 K, Δ χ| (T) is dominated by RKKY interactions which reduce the effective Kondo temperature T e k and result in spin glass ordering. In Δ χ⊥ (T) crystal field effects dominate. Both Δ χ (T)| and ⊥ can be described quantitatively.

Spin--spin interaction interpretation of results in Zn--Mn

Abstract: We suggest that a crystal field interpretation of susceptibility paramagnetic resonance and specific heat results in Zn−Mn is not consistent and that ion-ion interactions more readily account for observed behavior. Using a spin-spin interaction model we find the exchange to be both anisotropic and dependent on more than ion first-nearest-neighbor interactions alone. Cluster contributions are found in both the specific heat and susceptibility.