摘要:

Permanent magnets made from SmCo5exhibit negative reversible change in magnetization with increasing temperature, typically of the order of 0.04&percent; per deg. C. between −100 and +200 C. It is desirable to improve this property by suitable substitutions. In the present study, a systematic examination of the preparation, structural and magnetic characterization of SmxR1−xCo5(R=Tb, Dy and Er) has been undertaken. The ternaries were prepared by induction melting of the metals of proper stoichiometries. Magnetic studies were performed between 4.2 and 1000 K in applied fields up to 20 kOe. The results indicate that the best temperature compensation is achieved in the ternary SmxDy1−xCo5. Saturation magnetization and Curie temperatures are also reported.

ISSN:0021-8979    

DOI:10.1063/1.324742

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Heavy rare earth substitution for Sm in SmCo5magnets were carried out with a view of improving the reversible temperature coefficient (RTC) of magnetization. The RTC was found to vary depending on the temperature ranges of interest. Over the range of −50 C to +100 C for Sm0.6Dy0.4Co5and Sm0.68Er0.08Ho0.08Dy0.08Gd0.08Co5an RTC of +0.0062&percent; per °C and −0.0045&percent; per °C respectively was obtained with a (BH)maxexceeding 11 MGOe.

ISSN:0021-8979    

DOI:10.1063/1.324743

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The variation of coercive force as a function of annealing temperature is reported for some compacts of Co5Sm and Co5Pr alloys with the compositions of 63∼64 wt&percent; Co‐Sm and 60∼64 wt&percent; Co‐Pr, respectively. For the magnets made of these alloys, the curves of intrinsic coercive force against annealing temperature have two peaks; one at around 1080 °C and the other at 1190 °C in the Co‐Sm sintered magnets. The curves of coercive force in sintered Pr‐Co alloys have also two peaks; one near 1040 °C and the other near 1125 °C. This behavior can be correlated with the peritectic temperatures in the Co‐Sm and Co‐Pr phase diagrams. It is interpreted in terms of a model which assumes the existence of the pinning sites for the domain walls and their concentration at boundaries between the precipitates and grains of Co5Rduring the sintering. These precipitates are thought to consist of otherR‐Co compounds with lower melting points thanRCo5.

ISSN:0021-8979    

DOI:10.1063/1.324744

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We review the dc transport properties of mixed valent compounds SmB6and gold‐SmS and find the character of the ground state, metallic or insulating, to be an open question. The room temperature optical properties of SmB6and gold‐SmS display ordinary metallic behavior at high energy, but are very nonmetallic at low energy in thatE1becomes positive like an insulator from about 0.1 eV down to the lowest energy measured. We show that these room temperature optical properties are consistent with a ’’bad‐metal’’ model having either a sharp 4fresonance at the Fermi level, or a collective low frequency density fluctuation, and extract from the data a value ∼.08 eV for the 4f‐5dmixing matrix element. But we point out that the possibility of an insulating ground state remains.

ISSN:0021-8979    

DOI:10.1063/1.324745

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A theoretical approach to the problem of configuration fluctuation in Sm chalcogenides is presented. Properties of the fluctuating valence phase (also referred to as the collapsed phase) are discussed within an essentially localized model (ELM) in which most of the Sm 5delectrons are localized and only a small number (?0.1 electrons per Sm) occupy the free‐electron‐like states at the bottom of ad‐band. We argue that the ELM for the collapsed phase of SmS can account for almost all and, as far as we know, is inconsistent with none of the available experimental data.

ISSN:0021-8979    

DOI:10.1063/1.324746

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The coherent potential approximation (CPA) is applied to the description of intermediate valence induced by alloying as observed in the solid solutions Sm1−xRxS whereRdenotes a rare‐earth element which is trivalent in the monosulfide. The description is based on the Falicov‐Kimball model for metal‐insulator transitions generalized to take into account the disorder associated with theRsubstitution. This disorder is treated within the CPA while the intra‐atomic correlation on the Sm sites is also treated by the CPA in analogy with an alloy of divalent and trivalent Sm ions. The transition to an intermediate valence for Sm as a function of alloy composition is discussed in terms of the results of this treatment.

ISSN:0021-8979    

DOI:10.1063/1.324747

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Magnetic susceptibility measurements of a series of SmSbxS1−xsolid solutions are reported. The results for the Sb‐rich alloys provide evidence for the disappearance of magnetic ordering in a Sm system which exhibits intermediate valence. The magnetic susceptibility of SmSb where Sm is trivalent (4f5configuration) shows an antiferromagnetic transition withTN=2.8 K. With increasing substitution of S for Sb there is a rounding of the cusp in the susceptibility at 2.8 K indicating the disappearance of the antiferromagnetic transition. This is attributed to configuration mixing (4f5and 4f6) where the Sm has homogeneous intermediate valence. An estimate of the intermediate valence as a function of the S concentration is provided by lattice constant measurements.

ISSN:0021-8979    

DOI:10.1063/1.324748

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The susceptibility of YbxSc1−xAl3(Cu3Au‐type structure) forx=0.1, 0.2, 0.5 and 1.0 has been measured from 4.2 to 700 K. In contrast to Ce‐Th alloys, the addition of a smaller atom, Sc, to YbAl3favors the configuration with a larger atomic volume, Yb2+. The susceptibility per mole Yb exhibits a broad maximum which shifts to lower temperatures with increasingx. Room temperature lattice constant measurements indicate that the valance increases gradually from ∼2.7 atx=0.1 to ∼2.9 atx=1.0. Fitting our data to the resonant level‐type model of Sales, we find that the width of the resonant level ‐ decreases dramatically with increasingx. All the data approximately satisfies a scaling relationship.

ISSN:0021-8979    

DOI:10.1063/1.324749

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Crystals of EuSm2S4and SrSm2S4having the cubic Th3P4structure are insulators, with a random distribution of Sr2+and Sm3+over equivalent sites. EuSm2S4is a ferromagnet withTc=2.7 K. SrSm2S4does not order magnetically above 1.4 K. A sharp upturn in its specific heat below 4 K is attributed to splitting of the &Ggr;8quartet by a small non‐cubic crystal field.

ISSN:0021-8979    

DOI:10.1063/1.324750

出版商:AIP    

年代:1978

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.324752

出版商:AIP    

年代:1978

数据来源: AIP