[en] Published in summary form only

No abstract available

No abstract available

[en] Highlights: •A positive value of ΔS_M for TbMn₂ is 8.3 J kg⁻¹ K⁻¹ under the field change of 0.1 T. •The maximum ΔS_M for ErMn₂ is 13.4 J kg⁻¹ K⁻¹ under the field changes of 0.2 T. •The maximum ΔS_M for ErMn₂ is 25.5 J kg⁻¹ K⁻¹ under the field changes of 0.5 T. •The RC for HoMn₂ is 404.3 J kg⁻¹ under the field changes of 0.5 T. •The larger ΔS_M and RC are not thermal and magnetic hysteresis loss. -- Abstract: Magnetocaloric effect (MCE) of RMn₂ (R = Tb, Dy, Ho, Er) compounds are investigated. TbMn₂ and DyMn₂ crystallize in cubic Laves phase structure (C15 type), whereas HoMn₂ and ErMn₂ crystallize in hexagonal Laves phase structure (C14 type). For TbMn₂ compound, the field-induced metamagnetic transition accompanying a spontaneous cell volume expansion is observed (inverse MCE), which leads to a large positive value (8.3 J kg⁻¹ K⁻¹) of magnetic entropy change around 36 K under the field change of 0–1 T, while the maximal values of magnetic entropy change (ΔS_M) and the refrigerant capacity (RC) for other RMn₂ (R = Dy, Ho, Er) compounds are −15.7, −18.4, −25.5 J kg⁻¹ K⁻¹ and 403.6, 404.3, 316.0 J kg⁻¹ around their T_C with negligible thermal and magnetic hysteresis loss for the field change of 0–5 T, respectively. The results suggest that RMn₂ (R = Dy, Ho, Er) may be appropriate candidates for magnetic refrigerant working at low temperature region 10–80 K

[en] Short communication

[en] The reported value of the heat of formation of UFe₂ determined by acid solution calorimetry and the Gibbs energy of formation determined by high temperature emf cells give results that are in poor agreement. A well defined correlation exists between the heat of formation and the unalloyed radius ratio of AB₂ type Laves compounds. When this test is applied it is found that the emf data of Yoshihara and Kauno for UFe₂ give good correlation with the compounds formed between Pu and the Group VIIIa metals. These authors did not indicate that heats or entropies of formation could be calculated from their data, a third law calculation using Kopp's low of the additivity of heat capacity shows that the entropy term derived from the observed Gibbs energy of formation is reasonable. The thermal functions were calculated in this manner after making a small correction for the Curie point anomaly in Fe at 1033 K. The Curie point of UFe₂ was estimated to be 193 K. The thermodynamic functions are given and were calculated from the Gibbs energies of formation at 1000 K

[en] Early expectations that the proximity of the 5f band to the Fermi level would lead to complex magnetic (or almost magnetic) behaviour were correct. Well documented examples of spin-fluctuation systems, itinerant and localized magnetic systems now exist. Rather than attempt a complete survey of the experimental results, this review focusses on three systems of major importance; (a) the elements, (b) Laves phase compounds, and (c) NaCl-type compounds. In (a) the main advances have come in theories to explain the unusual resistivities of the elements and in the positive identification that curium metal is antiferromagnetic with T/sub N/ = 52⁰K. In (b) experiments on materials such as UAI₂ have shown ''idealized'' spin fluctuation behaviour whereas in the Np compounds simple arguments related to the Np-Np spacing lead to at least a qualitative understanding of the magnetic behaviour. In AmFe₂ we may have detected the first example of a mixed valence state, Am²⁺-Am³⁺. Finally a number of ''second generation'' experiments on actinide rock salt compounds will be reviewed. Contrary to earlier ideas, not all these systems can be understood with a localized model. This is especially true of the uranium compounds with small lattice spacings like UN, US and probably UC. On the other hand, for USb and compounds with transuranium elements the localized model will probably apply, e.g. PuP and AmSb

[en] This contribution focuses on the structural and physical properties of U-based Laves phases. It starts with the structural description of the different type of Laves phases, followed by a brief description of the factors that affect their stability. The majority of the uranium Laves phases show a weakly paramagnetic behaviour. The reason is the compact structure of the phases that leads to small a U-U spacing as well as very high coordination numbers, regarding both the uranium and the ligands sublattices, which brings a strong hybridization with non-f states. However, there are some exceptions of uranium Laves phases that do order magnetically (UFe₂, UNi₂ and the recently discovered U₂Fe₃Ge compound). These exceptions are discussed in more detail in the present manuscript.

[en] This talk will summarize the detailed alloy design strategy of creep-resistant, alumina-forming austenitic (AFA) stainless steel alloys developed at Oak Ridge National Laboratory. The AFA alloy design was based on careful selection of alloying additions utilizing guidance from computational thermodynamics, which achieved formation of protective Al_2O_3 scales in high-temperature oxidizing environments and multiple second-phase precipitation for improved creep strength. The microstructure of AFA alloys primarily consists of an austenitic single-phase matrix together with MC (M: mainly Nb), M_2_3C_6 (M: mainly Cr), (Fe,Ni)Al-type B2, Fe_2(Nb,Mo)-type C14-Laves, and Ni_3Al-type L1_2 phases, depending upon the compositions and temperatures. Stable, coherent Ni3(X) phase precipitate dispersions showed the best creep strength among the developed AFA alloys and comparable to that of Ni-base alloys in the temperature range of 700-750°C. Cast versions of AFA have also been developed which possess good creep resistance comparable to that of a traditional chromia-forming, cast austenitic stainless steel (HK) at temperatures up to 750°C. Development efforts to increase the temperature limit above 900°C are currently in progress. (author)

[en] We report measurements of the field-induced magnetization density in CeRu₂. The main results of the study are that the magnetic density is located equally at the Ce and Ru sites, and that the distribution of the induced magnetization about the Ce site extends to larger distances than predicted for Ce³⁺ ions with well localized f electrons. Our measurements also cover the superconducting state, where we do not observe any suppression of the spin susceptibility. In an accompanying structural study (in zero field) of our single crystal we detect a small deviation from the ideal Laves phase structure. These results are discussed in relation to the unusual electronic and magnetic properties of this compound. (author)