S. Methfessel

Sputtered NdFeB-films of high coercivity

Abstract Thin Nd(Dy)FeB-films prepared by rf-magnetron sputtering with different substrate temperatures and deposition rates were investigated for their magnetic and structural properties.

Magnetic ordering and electrical conductivity in La3−xS4, Gd3−xS4 and Ce3−xS4

Abstract An increase of the ferromagnetic Curie temperatures with increasing conduction electron concentration known for Gd 3− x S 4 is observed also in Ce 3− x S 4 . We determined the magnetic influence on the conduction electron scattering by comparing the resistivity of these compounds with the results for the nonmagnetic La 3− x S 4 . The magnetic contributions to the resistivity vary strongly with conduction electron concentration.

Magnetic and structural studies of the alloy system REIn0.5Ag0.5

Abstract The structural and magnetic properties of the alloy system REIn 0.5 Ag 0.5 [RE = Gd, Tb, Dy, Ho, Er, Tm and Yb] are reported. All these alloys (except that of Yb) crystallize in a cubic CsCl type structure at room temperature. Low temperature X-ray diffraction data does not reveal any structural phase transformation down to 8 K. On the basis of magnetic susceptibility data at a different temperature (3–300 K) and applied magnetic field (2 × 10 5 to 8 × 10 6 A m -1 , it has been concluded that GdIn 0.5 Ag 0.5 is ferromagnetic ( T c = 118 K), TbIn 0.5 Ag 0.5 and DyIn 0.5 Ag 0.5 are meta magnetic ( T N = 66 and 30 K, respectively) and alloys involving Ho, Er, Tm and Yb are ferrimagnetic with Neel temperatures ( T N ) equal to 24, 22, 21 and 20 K, respectively. The evaluated effective magneton number ( p ) is found to be slightly larger compared to theoretical values for tripositive ions of Gd, Tb and Dy and a bit smaller for Ho, Er, Tm and Yb. The results have been qualitatively explained using appropriate theories.

Magnetic properties of rapidly quenched (Nd2Fe14B)1−x(N d1.1Fe4B4)x alloys

Abstract Amorphous ribbons with the formal composition (T 1 ) 1− x (T 2 ) x (i.e. Nd 12±ϵ Fe 88 − y B y ) with T 1 = Nd 2 Fe 14 B and T 2 = Nd 1.1. Fe 4 B 4 and 0≤ x ≤1.0 were prepared by a single roller quenching apparatus. The Curie temperature T c and crystalliz ation temperature T cr of the samples and the effects of heat treatment on their magnetic properties and microstructure were studied. The concentration dependence of T c is found to have a maximum value of 505 K and about x = 0.19 ( y = 13). The T cr increases rapidly with increasing x , goes through a maximum to lower values, then rises again. The X-ray diffraction measurements show that the crystallized samples consist of T 1 and T 2 . In the electron diffraction microscope we see well defined grains of T 1 and T 2 which have an average size of about 650 A for T 1 and about 1500 A for T 2 after annealing at 700–800°C. The coercivity under optimal annealing condition is found to be approximately constant with increasing concentration x of the nonmagnetic T 2 phase. An intrinsic coercivity of 8.6 kOe and an energy product of 12 MGOc in Nd 2 Fe 14 B are obtained at room temperature by annealing at 800°C for 10 min.

Temperature dependence of the magnetic hysteresis properties of some Metglasses between 4•2 and 300 K

Abstract We report on measurements of magnetic hysteresis loops and initial permeability of amorphous metals with composition Fe81.5B14.5Si4, Fe40Ni40B20, Fe39Ni39(SiB)20 and Co67Fe4Mo2(SiB)27 in the temperature range between 4.2 and 300 K. For one sample (Fe40Ni40B20) the coercive force and the permeability are only weakly temperature dependent. The other samples show an increase in the coercive force up to a factor 3 and a decrease of the permeability up to a factor 10 in the temperature range below 70 K. The results are discussed within the framework of the statistical potential theory for Bloch wall movements.

Magnetic clusters in dilutions of EuS

Abstract The spin glass like properties of Eu x Sr 1−x S are found to be very sensitive to preparation conditions (fine powder, evaporated films and single crystals). Chemical clustering is of particular importance because the reach of exchange forces is restricted to one unit cell. Preliminary results indicate the trend of spinodal decomposition in single crystals with concentrations 0.15 Ṽ x ⪷ 0.85.

Stability of Sm2+ in Sm1−xRE3+xS

Abstract Critical concentrations and transition temperatures in Sm1−xRE3+xS have been investigated for several RE3+ -substituents. The valency υ of Sm in the metallic state is a more relevant parameter for the description of the phase transformation than the ionic size. It is related to the hybridization of local 4f-levels with 5d-conduction states.

Appearance potential spectroscopy of the lanthanides

Abstract Measurements on lanthanide metals determine the position of the unoccupied 4f levels. The observed difference in energy between the unoccupied 4f states and the Fermi level E F decreases monotonically with increasing atomic number for the light lanthanides. The 4f level lies near E F in Sm metal and far above E F in Eu.

Magnetooptical redshift in EuxSr1−xS

Abstract The magnetooptical redshift of the absorption edge and the photoluminescence emission peak is used to analyse the magnetic short range ordering in Eu x Sr 1− x S. Ferromagnetic short range ordering exists in the whole concentration range x > 0.2. At the critical concentration for long range ferromagnetic ordering x c = 0.52 there is a characteristic decrease of the ferromagnetic short range ordering.

Ein verfahren zur messung der gleichfeld-magnetostriktion von elektroblechen

Zusammenfassung Der Wegaufnehmer U/80 der Firma UniMeasure wird zur Messung der Gleichfeld-Magnetostriktion von Elektroblechen der Abmessungen 70 × 10 mm2 benutzt. Der Wegaufnehmer nutzt die Anderung des elektrischen Widerstands eines Halbleiters in einem magnetischen Feld aus. Die Anderung des Widerstandes wird mit einer Vierpunktmethode gemessen. Eine Auflosung von Δl l = 10 -7 oder 4 nm wird erreicht. Thermische Ausdehnung der Probe durch die Joulsche Warme des Erregerstromes kann numerisch kompensiert werden.