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The magnetic ordering of polycrystalline Ho 6 Co 2 Ga-type Gd 6 Co 2.2 Al 0.8 , Tb 6 Co 2.2 Al 0.8 , Tb 6 Co 2 Al and Dy 6 Co 2.2 Al 0.8 (space group Immm , N 71, oI 36) has been established using magnetic measurements and the magnetic structure of Tb 6 Co 2.2 Al 0.8 has been resolved by the neutron diffraction study. Gd 6 Co 2.2 Al 0.8 exhibits field sensitive ferro-antiferromagnetic ordering, meanwhile Tb 6 Co 2.2 Al 0.8 , Tb 6 Co 2 Al and Dy 6 Co 2.2 Al 0.8 are antiferromagnets with metamagnetic transformation of magnetic ordering. Gd 6 Co 2.2 Al 0.8 is soft ferromagnet, whereas Tb 6 Co 2.2 Al 0.8 , Tb 6 Co 2 Al and Dy 6 Co 2.2 Al 0.8 exhibit low-temperature weak permanent magnet properties. From these compounds, Gd 6 Co 2.2 Al 0.8 demonstrates largest magnetocaloric effect with magnetic entropy change of −10.89 J/kg⋅K at 75 K for a field change of 50 kOe (relative cooling power of ~760 J/kg). Neutron diffraction study indicates non-collinear abc -antiferromagnetic ordering of Tb 6 Co 2.2 Al 0.8 in zero applied magnetic field. Below 63 K and down to 52 K, Tb 6 Co 2.2 Al 0.8 exhibits antiferromagnetic ordering with magnetic space group I′22′2′ (wave vector K 0 = [0, 0, 0]). Below 52 K and down to 1.5 K, the magnetic structure of Tb 6 Co 2.2 Al 0.8 is sum of magnetic component with P2 1 ′2 1 2′ magnetic space group (wave vector K 0 = [0, 0, 0]) and square-modulated antiferromagnetic component along c -axis of unit cell with K 1 = [±1/4, 0, ±1/4] wave vector. Image 1 • Gd 6 Co 2.2 Al 0.8 shows F-AF ordering and it is soft ferromagnet down to 2 K. • Δ S m of Gd 6 Co 2.2 Al 0.8 reaches of −10.89 J/kg⋅K at 75 K in field change of 50 kOe. • Tb 6 Co 2.2 Al 0.8 , Tb 6 Co 2 Al and Dy 6 Co 2.2 Al 0.8 show field sensitive AF ordering. • Tb 6 Co 2.2 Al 0.8 , Tb 6 Co 2 Al and Dy 6 Co 2.2 Al 0.8 are LT weak permanent magnets. • Tb 6 Co 2.2 Al 0.8 exhibits abc -Antiferromagnetic ordering in zero applied field. [ABSTRACT FROM AUTHOR]

The magnetic ordering of Mo 2 NiB 2 -type {Gd, Tb, Dy} 2 Co 2 Al ( Immm , No. 71, oI 10) compounds has been established using bulk magnetic measurements and neutron diffraction study. Polycrystalline Gd 2 Co 2 Al, Tb 2 Co 2 Al and Dy 2 Co 2 Al undergo ferrimagnetic transitions (T C ) at 78 K, 98 K and 58 K, respectively, and low-temperature field induced transition (T m ) around 15 K, 20 K and 15 K, respectively. Between T m and T C Gd 2 Co 2 Al, Tb 2 Co 2 Al and Dy 2 Co 2 Al are soft ferrimagnets. Below T m Gd 2 Co 2 Al is soft ferrimagnet, whereas Tb 2 Co 2 Al and Dy 2 Co 2 Al exhibit permanent magnet properties with residual magnetization per rare earth of 4.95 B and 4.8 B , respectively, and large coercive field of 72 kOe and 22 kOe, respectively, at 2 K. The magnetocaloric effects of Gd 2 Co 2 Al, Tb 2 Co 2 Al and Dy 2 Co 2 Al were calculated in terms of isothermal magnetic entropy change and they reach maximum values of −10.4 J/kg K, −7.6 J/kg K and −6.6 J/kg K for a field change of 50 kOe near 75 K, 98 K and 58 K, respectively. Low-temperature transition of Gd 2 Co 2 Al is followed by the magnetic entropy change of −2.9 J/kg K in a field change of 50 kOe at 15 K. Low temperature magnetic ordering with enhanced anisotropic effects in Tb 2 Co 2 Al and Dy 2 Co 2 Al is accompanied by a positive magnetocaloric effect with isothermal magnetic entropy changes of +19.9 J/kg K at 20 K (field change 0–50 kOe) and +2.7 J/kg K at 15 K (field change 0–10 kOe), respectively. Neutron diffraction study shows that, in zero applied field, Tb 2 Co 2 Al exhibits c -axis ferrimagnetic ordering with magnetic space group Immm ′ and propagation vector K 0 = [0, 0, 0] below T C ND ∼ 111 K with M Tb = 8.86(15) B and M Co = 0.26(2) B at 2 K. [ABSTRACT FROM AUTHOR]

An investigation of the two-component phase diagram of the CaNaPO 4 - CaKPO 4 system performed using various analysis techniques is reported. The continuous solid solution series of α-CaMPO 4 existing above 700 °C undergoes eutectoid decomposition during cooling to β-CaMPO 4 -based solid solutions enriched with Na and K, and to an intermediate nonstoichiometric compound with an ideal composition of CaK 0.6 Na 0.4 PO 4. All three compounds exhibit significant volumetric effects associated with first-order phase transitions, with positive volume changes under cooling for the intermediate compound. Increased K content in ceramics based on CaK y Na 1- y PO 4 compositions enhances the strength properties of those ceramics, including their fracture toughness, which is associated with increased density. Increased K content also has a smaller effect of inducing phase transformations accompanied by strong volume changes. [ABSTRACT FROM AUTHOR]

Abstract: The temperature dependence of electrical conductivity and magnetoconductivity of new type of carbon films composed of nanosize thin graphite-like crystallites were investigated at temperature interval of 4.2–300K and in the magnetic field range of 0–12kG at 4.2K, respectively. The crystallites consist of several (5–50) graphene layers which have predominant orientation perpendicularly to a film surface. At temperature ≤30K the logarithmic conductivity decreases linearly with temperature. The positive magnetoconductivity of the films was observed in a magnetic field directed perpendicularly to the film surface in all intervals of field values. In magnetic field B≥4kG the logarithmic asymptotic of conductivity from magnetic field was observed. That is characteristic of the systems with two-dimensional quantum corrections to magnetoconductivity. In a magnetic field directed along a film surface, the crossover from negative to positive magnetoresistivity is observed at B≥8kG. [Copyright &y& Elsevier]

The magnetic and magnetocaloric properties of the intermetallic family (Gd,Tb) 6 (Fe,Mn)Bi 2 have been studied from 2 K to temperatures above the respective Curie temperatures T C. The substitution of Gd by Tb (Gd 6 FeBi 2 , Gd 3 Tb 3 FeBi 2 , Tb 6 FeBi 2) tunes T C in the range 350-250 K and favors the apparition of a metamagnetic transition at very low temperature (below 10 K) from a complex magnetic state to a ferromagnetic one, as well as a spin reorientation transition below T m = 72 K. As a consequence, an important inverse magnetocaloric effect (IMCE) appears below 20 K and an interesting direct magnetocaloric effect (DMCE) appears over a wide temperature span between T C and T m with maxima at those temperatures. The partial substitution of Fe by Mn in Tb 6 Fe 0.5 Mn 0.5 Bi 2 shifts these effects upwards in temperature while expanding the region of the direct magnetocaloric effect between 70 and 400 K. The combination of adjoint IMCE and DMCE as well as the wide span of the latter shows that tuning this family allows to locate the magnetocaloric effect in different regions of interest. The critical behavior of the PM-FM transitions has been studied obtaining the critical exponents α, β, γ, δ and checking that the respective magnetocaloric effects also scale with the critical parameters n and δ. The transition in Gd 6 FeBi 2 belongs to the Heisenberg universality class with deviations due to magnetocrystalline anisotropies; the critical exponents for Gd 3 Tb 3 FeBi 2 (in agreement with the Mean Field model) suggest the presence of long range order magnetic interactions, while Tb 6 FeBi 2 and Tb 6 Fe 0.5 Mn 0.5 Bi 2 present an unconventional critical behavior aligned with long range order interactions. • Gd by Tb substitution tunes T C and improves the magnetocaloric properties. • Tb samples present two main transitions and extended temperature working range. • Adjoint inverse and direct magnetocaloric effects in Td-doped compounds. • Critical exponents α, β, γ, δ found for the PM-FM transition. [ABSTRACT FROM AUTHOR]

Application of porous anodic alumina as membranes and templates is restricted by its rapid degradation in acidic and alkaline media. Chemical stability of the anodic alumina could be strongly enhanced by annealing leading to crystallization of as-prepared amorphous material into a mixture of low-temperature Al 2 O 3 polymorphic modifications and then to α-Al 2 O 3 phase. Here an approach to choosing an annealing protocol for crystallization of porous anodic alumina into the corundum phase preserving its starting morphology is suggested. Formation of corundum films with hexagonally-packed 27-nm-diameter channels by multi-step annealing of anodic alumina prepared in 0.3 М sulfuric acid at 25 V is demonstrated. According to electron backscatter diffraction, α-Al 2 O 3 films consist of porous single-crystalline grains with an average size of ~ 5 ÷ 10 μm. Crystallization of α-Al 2 O 3 phase from amorphous anodic alumina results in the enhancement of its chemical stability by two orders of magnitude in comparison with porous films consisting of low-temperature polymorphic modifications of Al 2 O 3. Image 1 • Approach to choosing an annealing protocol for anodic alumina is suggested. • Alpha-alumina films with an ordered arrangement of sub-30 nm pores are obtained. • Coarse-grain structure of porous corundum films is proved by EBSD. • Chemical stability of γ-Al 2 O 3 and α-Al 2 O 3 porous films is compare. [ABSTRACT FROM AUTHOR]