R. S. Craig

MAGNETIC CHARACTERISTICS OF SOME BINARY AND TERNARY 2--17 COMPOUNDS.

The magnetic anisotropy of R2Co17 and R2Co17−xTx compounds with R=Y, Ce, Pr, Nd, Th and T=Mn, Fe has been investigated. The directions of easy magnetization were determined by x‐ray studies on oriented powders. The several R2Co17 compounds, except for Ce2Co17, have an easy basal plane; the behavior of Ce2Co17 could not be clarified. Replacement of Co by Mn or Fe changes the easy magnetization direction from the basal plane to the c axis. Anisotropy fields were measured on magnetically aligned powders. The values for the anisotropy fields range between 12 and 24 kOe. Curie temperatures and saturation magnetization data for R2Co17−xTx compounds with T=Mn, Ru and R=Ho, Y are reported. The decrease of the magnetization with increasing x observed in the system Y2Co17−xTx is accounted for by assuming either a reduced Co moment or an antiparallel coupling of the T transition‐metal spin. Similar considerations hold for Ho2Co17−xTx ternaries.

Magnetic and Electrical Characteristics of REPd3 Intermetallic Compounds

Magnetic characteristics of 12 REPd3 (RE = a rare earth) compounds have been studied between 4° and 300°K. Electrical resistivity measurements have been made on the Ce, Gd, and Ho compounds. All compounds are paramagnetic at room temperature; all except CdPd3, SmPd3, and EuPd3 exhibit Curie‐Weiss behavior with paramagnetic moments in close agreement with that expected for the free tripositive ion. The susceptibility behavior of CePd3 is ascribed to the Kondo phenomenon (spin compensation) while that of SmPd3 and EuPd3 to the narrowness of the multiplet spacings. This interpretation for CePd3 is supported by its resistivity‐temperature behavior. Evidence for magnetic ordering is found only for GdPd3, which seems to order ferromagnetically below 7°K.

Magnetic properties of RT3−x′Nix compounds (R=Dy or Ho and T′=Fe or Co)

The effect of varying electron concentration on the magnetic ordering in the ternary intermetallic compounds DyCo3−xNix, DyFe3−xNix, HoCo3−xNix, HoFe3−xNix, with 0<x<3, has been investigated by saturation magnetization studies. The results show a filling of the Co and Fe bands and also a polarization of the 3d band of nickel. In the case of the Co compounds an additional contribution from the induced moment on cobalt by the rare‐earth exchange field is found to be important.

Heat Capacity of Glycerol Glass Between 1.5° and 4°K. Use of Glycerol as a Heat Exchange Medium in Low‐Temperature Calorimetry

The heat capacity of glycerol glass was measured between 1.5° and 4°K. Below 2°K the heat capacity is in excess of that expected from theoretical considerations for an isotropic solid. The use of glycerol as a heat exchange medium is discussed and described.

STRUCTURAL AND MAGNETIC CHARACTERISTICS OF DYSPROSIUM-YTTRIUM SOLID SOLUTIONS

X‐ray studies have shown that dysprosium and yttrium are miscible in all proportions in the solid state at room temperature. Vegards law is approximately obeyed.Thermomagnetic analyses were carried out between 4°K and room temperature and the field dependencies were measured at liquid He, liquid N2, and room temperature on alloys containing from 10 to 95 at.% Dy. Alloys containing less than 90 at.% Dy are paramagnetic at room temperature and antiferromagnetic at lower temperatures with no clear evidence of ferromagnetism down to liquid He temperatures. The Neel point (TN) decreases with decreasing Dy content, TN32 varying linearly with composition.Alloys containing 90 and 95 at.% Dy are ferromagnetic at low temperatures. When the samples were cooled to 4°K in the absence of a field and the magnetization measured as the sample warmed up in a field, it was observed that the moment was initially low as if the sample were antiferromagnetic (or at least nonferromagnetic). With increasing temperature the momen...

Magnetic properties of DyFe3−xCox and HoFe3−xCox*

Abstract Magnetic moments, Curie and compensation temperatures were measured for DyFe 3−x Co x and HoFe 3−x Co x compounds. The variation of transition metal moment has been explained on the basis of the rigid band model.

Influence of the crystalline electric field on the heat capacity and resistivity of PrAl3

Results of heat‐capacity and resistivity measurements performed on PrAl3 between 1.5 and 300 K are utilized to reveal and characterize the influence of the crystalline electric field on the ground‐state multiplet of Pr+3 in PrAl3. Also reported are the results of heat‐capacity measurements on the isostructural nonmagnetic counterpart LaAl3 for which there are only vibrational and electronic contributions to Cp. Below 180 K, the excess heat capacity of PrAl3 over that of LaAl3 exhibits of Schottky‐type thermal anomaly peaking at 25 K and is attributable to excitation within the crystal‐field states. Resistivity results indicate a temperature‐dependent spin‐disorder contribution at low temperatures associated with the splitting of the ground‐state multiplet by the crystal field. The higher‐temperature resistivity behavior is observed to be a linear function of temperature and can be readily assigned to phonon contribution. The crystal‐field interaction is analyzed using the crystal‐field Hamiltonian, HCF=W2...

Heat capacities and related thermal properties of DyNi5, HoNi5 and ErNi5 between 5 and 300 K☆

Abstract Heat capacity data and calculated thermodynamic functions are presented for DyNi 5 , HoNi 5 and ErNi 5 . λ-type thermal anomalies are noted at 12.0 K (DyNi 5 ), 4.1 K (HoNi 5 ) and 8.0 K (ErNi 5 ). Schottky-type anomalies are observed at higher temperatures. The λ and Schottky anomalies are ascribed to the destruction of ferromagnetic order and to crystal field excitation, respectively. A deficiency of magnetic entropy, compared to R ln(2 J + 1), is noted corresponding roughly to R ln2. This suggests that the ground state in the ordered materials is a doublet. ErNi 5 is analyzed using a Hamiltonian containing terms representing the crystal field and magnetic interactions. The analysis shows that a doublet ground state can result with reasonable values of the crystal field parameters. The parameters are shown to be consistent with the heat capacity behavior of ErNi 5 . Ordering temperatures are not proportional to the de Gennes function.

Effect of dissolved hydrogen on the electrical and magnetic behavior of PrCo2 and NdCo2

Abstract When retained hydrogen is removed from PrCo 2 and NdCo 2 these compounds remain paramagnetic to temperatures well below their normal Curie temperatures. Abstraction of the hydrogen seems to weaken exchange, depressing T c by about 40° for PrCo 2 and 110° for NdCo 2 .

Spin polarization effects in Nd1-xHoxCo3 compounds

Abstract Magnetic moments and Curie temperatures have been measured for Nd 1- x Ho x Co 3 compounds. The cobalt moment has been found to be non-linear with x . This effect is attributed to spin polarization.