Caracterização magnética dos sistemas DYRHIN5 e DY2RHGA8

Abstract

In this dissertation we present the synthesis of intermetallic compounds DyRhIn5 and Dy2RhGa8, in single crystalline shape by self-flux method, the structural characterization was done by powder X-ray diffraction measurements at room temperature and the magnetic characterization by dc magnetization measurements as a function of temperature and magnetic field applied in two directions, along and perpendicular to the c-axis of single crystals, using a commercial magnetometer MPMS-7 with SQUID detection. The single crystal was formed in a single phase with tetragonal structure HoCoGa5-type, belonging to the space group P4/mmm, with lattice parameters equals to a = b = 4.585 Å and c = 7.359 Å. This compound showed an antiferromagnetic order with Néel Temperature of 28 k when the magnetic field of 1 kOe was applied along to the c-axis. In the magnetic hysteresis curves at T = 2 and 5 K, with the magnetic field applied parallel to the c-axis, a metamagnetic behavior was observed for magnetic fields above 50 kOe. The Dy2RhGa8 compound was growth in phase purity with tetragonal structure Ho2CoGa8-type, belonging to space group P4/mmm, with lattice parameters equals to a = b = 4.332 Å and c = 11.347 Å. An antiferromagnetic order was observed with the Néel temperature of 11 k when the magnetic field was applied in both directions. We observed a typical Curie-Weiss behavior above Néel Temperature for both compounds, signalizing the localized moment of Dy3+ ion. The magnetic susceptibility data were analyzed by means of crystalline electric field (CEF) in these dysprosium compounds. From the data we estimate the crystal field parameters, and discuss that the observed anisotropy can be attributed to CEF effects in Dy3+ ion in a tetragonal symmetry.