Chromium trihalides are layered and exfoliable semiconductors and exhibit unusual magnetic properties with a surprising temperature dependence of the magnetization. By analyzing the evolution of the magnetocrystalline anisotropy with temperature in chromium iodide CrI 3 , we find it strongly changes from K u = 300 ± 50 kJ/m 3 at 5 K to K u = 43 ± 7 kJ/m 3 at 60 K, close to the Curie temperature. We draw a direct comparison to CrBr 3 , which serves as a reference, and where we find results consistent with literature. In particular, we show that the anisotropy change in the iodide compound is more than 3 times larger than in the bromide. We analyze this temperature dependence using a classical model, showing that the anisotropy constant scales with the magnetization at any given temperature below the Curie temperature, indicating that the temperature dependence can be explained by a dominant uniaxial anisotropy where this scaling results from local spin clusters having thermally induced magnetization directions that deviate from the overall magnetization.

We report on detailed Hall-effect measurements of thin films of La 0.67 Ca 0.33 MnO 3 above and below the metal-insulator transition. In the metallic ferromagnetic regime, we find a temperature-independent holelike nominal charge-carrier density n h *ϭ1.3 per unit cell, consistent with a partly compensated Fermi surface. The mobility is only 92 mm 2 /V s at 4 K, and decreases with increasing temperature. Huge negative magnetoresistivity results from an increase in mobility. In low magnetic fields or at high temperatures, an anomalous electronlike contribution dominates the Hall voltage. For possible side jumps, we estimate an average jump length of the electron wave packet of 10 Ϫ13 m.

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We prepared epitaxial ferromagnetic manganite films on 45 • bicrystal substrates by pulsed laser ablation. Their low-and high-field magnetoresistance (MR) was measured as a function of magnetic field, temperature and current. At low temperatures hysteretic changes in resistivity up to 70 % due to switching of magnetic domains at the coercitive field are observed. The strongly non-ohmic behavior of the current-voltage (I-V ) leads to a complete suppression of the MR effect at high bias currents with the identical current dependence at low and high magnetic fields. We discuss the data in view of tunneling and mesoscale magnetic transport models and propose an explicit dependence of the spin polarization on the applied current in the grain boundary region.

We measured the temperature dependence of the linear high field Hall resistivity ρH of La0.67Ca0.33MnO3 (TC = 232 K) and La0.67Sr0.33MnO3 (TC = 345 K) thin films in the temperature range from 4 K up to 360 K in magnetic fields up to 20 T. At low temperatures we find a charge-carrier density of 1.3 and 1.4 holes per unit cell for the Ca-and Sr-doped compound, respectively. In this temperature range electron-magnon scattering contributes to the longitudinal resistivity. At the ferromagnetic transition temperature TC a dramatic drop in the number of current carriers n down to 0.6 holes per unit cell, accompanied by an increase in unit cell volume, is observed. Corrections of the Hall data due to a non saturated magnetic state will lead a more pronounced charge carrier density collapse.