R.M. Galera

Magnetic and electrical properties of heusler alloys with rare earths: RInAg2

Abstract Rare earth ternary compounds RInAg2 were prepared for all rare earths except europium and ytterbium. They crystallized with a Heusler-type structure (L21). The magnetic properties and the electrical resistivity were studied in the temperature range 1.6–300 K. The paramagnetic susceptibilities showed Curie-Weiss behaviour for all the compounds except SmInAg2 which is a Van Vleck paramagnet. The asymptotic Curie temperatures θp were negative throughout the series. The cerium, neodymium, samarium, gadolinium, terbium and dysprosium compounds ordered antiferromagnetically at low temperatures, but no order was observed above 2 K in PrInAg2, HoInAg2, ErInAg2 or TmInAg2. Inelastic neutron scattering experiments were used to determine the crystal electric field parameters in the cerium, praseodymium and neodymium compounds.

Kondo lattice and heavy fermions in Heusler phases: CeInAg2−xCux

Magnetic properties, electrical resistivity, specific heat and magnetic excitations have been investigated in Heusler phases CeInAg2−xCux. The hybridization continuously increases from CeInAg2 (antiferromagnetic Kondo lattice) to CeInCu2 (heavy fermion compound). The specific heat coefficient for this last compound is found to reach 1.2 J/mole. K2 at 1.4 K, the Kondo temperature is 6 K and the Wilson ratio is close to 2.

Magnetic interactions and crystal field in RMg3 compounds (R = Ce, Pr, Nd)

Abstract We have carried out a study of magnetic properties, electrical resistivity and of crystal field excitations using inelastic neutron scattering, in cubic RMg 3 compounds with light rare earths R = Ce, Pr and Nd. The ground states are the Γ 7 and Γ 6 doublets for CeMg 3 and NdMg 3 , which order at 3.5 and 6.5 K, respectively. PrMg 3 has the non-magnetic Γ 3 ground state and remains a Van Vleck paramagnet. The magnetic contribution to the resistivity has been separated. It allows us to evaluate the couplings between the 4f shell and the conduction band which is much larger for CeMg 3 than for the other compounds. The coupling constant Γ is negative in this case, as shown by an incipient Kondo effect in this compound.

Magnetic susceptibility, electrical resistivity and neutron spectroscopy of some cubic cerium intermetallics

Reports a study of crystal-field (CF) excitations by neutron spectroscopy and a study of magnetic susceptibility and electrical resistivity of some cubic cerium intermetallics having the CsCl or a related structure; namely the compounds CeZn, CeMg3 and CeInAg2, CeZn undergoes a first-order transition to antiferromagnetism with a strong magnetostriction at TN=30K, whereas for CeMg3 and CeInAg2 (TN=3.4 and 2.3K respectively) the transition is of second order. The magnetic resistivities of the cerium compounds obtained by subtracting the resistivities of homologous lanthanum compounds were found to decrease with increasing temperature over certain temperature ranges, indicating an incipient Kondo effect. CeMg3 has a CF splitting Delta of 195K, the ground state being the Gamma 7 doublet in contrast to the case of the CeMg compound with its Gamma 8 ground state. For CeZn and CeInAg2, the CF splitting is rather small ( Delta approximately 65 and 18K respectively).

Magnetic properties of HfO2 thin films

We report on the magnetic and transport studies of hafnium oxide thin films grown by pulsed-laser deposition on sapphire substrates under different oxygen pressures, ranging from 10−7 to 10−1 mbar. Some physical properties of these thin films appear to depend on the oxygen pressure during growth: the film grown at low oxygen pressure (P≈10−7 mbar) has a metallic aspect and is conducting, with a positive Hall signal, while those grown under higher oxygen pressures (7 × 10−5≤P≤0.4 mbar) are insulating. However, no intrinsic ferromagnetic signal could be attributed to the HfO2 films, irrespective of the oxygen pressure during the deposition.

Investigation by neutron scattering of the high energy magnetic response in α-cerium and CePd3

Abstract The dynamical magnetic susceptibility has been measured in α-cerium up to energy transfers of 175 meV. The magnetic signal is small, no characteristic magnetic excitation occurs in this energy range. For CePd 3 , the magnetic response has a peak at 60 meV, which is attributed to the energy difference between magnetic and non-magnetic configurations.

Polarized neutron scattering in Kondo or intermediate valence compounds

Abstract Polarized neutron scattering with polarization analysis has been performed on α-cerium and CePd 3 . The magnetic response could be measured up to energy transfers of 250 meV. In CePd 3 , the response at 5 K is essentially inelastic and reveals a characteristic excitation at 65 meV. For Ce-α at 8 K, a significant signal appears in the range 200–250 meV. These inelastic excitations are attributed to transitions between hybridized mixed-valence states. From the characteristic energies, the experimental value of static properties χ(0) and γ can be reproduced, in the frame of recent theories of intermediate valence or Kondo systems.

Magneto-optical spectroscopy of (Ga,Mn)N epilayers

We report on the magneto-optical spectroscopy and cathodoluminescence of a set of wurtzite (Ga,Mn)N epilayers with a low Mn content, grown by molecular beam epitaxy. The sharpness of the absorption lines associated to the Mn

Magnetic spectral response in CeSi2

^{3+}

Magnetic structures of CeMg3, NdMg3 and CeInAg2

internal transitions allows a precise study of its Zeeman effect in both Faraday and Voigt configurations. We obtain a good agreement if we assume a dynamical Jahn-Teller effect in the 3d