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The sol–gel method is applied to prepare the polycrystalline La 0.8 Sr 0.2 MnO 3 manganite and to reduce grain sizes of nanocrystalline sample down to 23 nm. The magnetocaloric effect was determined from isothermal magnetization measurements. Transition from the polycrystalline to nanocrystalline structure reduces the size of magnetocaloric effect and markedly broadens the temperature interval over which it occurs. The relative cooling power RCP(S) = 35 J/kg in polycrystalline manganite remains almost the same in the nanocrystalline case.

The mechanical alloying method was used to prepare Co 60 Fe 30 Ni 10 and Co 50 Fe 35 Ni 15 alloys from the elemental powders. As X-ray diffraction studies proved the final products of milling were the solid solutions with b.c.c . lattice and the average grain size of about 60 nm. After heating of the alloys up to 993 K, the mixtures of two solid solutions with a b.c.c . and f.c.c . lattices were formed. Annealing of the alloys at 1173 K for 1 h resulted in the formation of solid solutions with an f.c.c . lattice. Mossbauer spectroscopy revealed hyperfine magnetic field distributions which reflected the different surroundings of 57 Fe isotopes by Co, Fe and Ni atoms, depending on the chemical composition of the alloy. The most probable atomic configurations were determined on the basis of a local environment model. The results of the macroscopic magnetic measurements testified that Co 60 Fe 30 Ni 10 and Co 50 Fe 35 Ni 15 alloys exhibited relatively good soft magnetic properties.

We compare structure and magnetic parameters of the polycrystalline and nanocrystalline manganites La 0.75 Ca 0.25 MnO 3 prepared by the carbonate precipitation and the sol–gel methods, respectively. The Curie temperature is surprisingly enhanced for nanocrystalline manganite. An effect of magnetic fields on transport parameters is analyzed for the metallic and semiconducting ranges.

The temperature variation of electrical resistivity is measured for amorphous and annealed Fe 73.5 Nb 4.5 Cr 5 Cu 1 B 16 alloys containing various fractions of nanocrystalline bcc-Fe grains embedded in the amorphous matrix. Crystalline fractions determined from magnetization and X-ray diffraction data for alloys annealed during 1 h at various temperatures are used to calculate the electrical resistivity of nanocrystalline grains from the Maxwell–Garnett relation.

X-ray diffraction analysis, differential scanning calorimetry and magnetization measurements were used to determine the structural changes of the Co 78 B 11 Si 11 alloys prepared by a ball milling of amorphous, crystallized ribbons and a mixture of elemental crystalline powders in vibratory mill. For all starting materials the high-energy ball milling of Co 78 B 11 Si 11 alloy produces a crystalline structure with nanometer sized crystals. The average crystallite size is about 5 nm. Three series of Co 78 B 11 Si 11 alloys are the ferromagnetic materials. Milling of amorphous alloys causes an increase of the room temperature magnetic moment from 0.90 to 1.08 μ B . A similar tendency is observed for alloys produced by milling of the initially crystallized ribbons for which the magnetic moment increases from 0.73 μ B at t = 0 to 1.17 μB after 250 h. Somewhat different dependence is found for alloys milled from powders since magnetization of the alloy subjected to longer milling is reduced by 10% due to structural disorder introduced during a formation of the crystalline Co(Si,B) phase with nanometer sized crystals.

We report on high-energy ball milling of Fe 78 B 13 Si 9 alloy prepared from amorphous and crystallized ribbons as starting materials as well as from a mixture of pure elemental powders. The X-ray diffraction (XRD), differential scanning calorimetry (DSC), magnetization and Mossbauer measurements were carried out. High-energy ball milling processes form nanocrystalline Fe-based solid solution for all starting materials investigated. The average grain size was in the range 8–16 nm. By mechanical crystallization of amorphous Fe 78 B 13 Si 9 alloy we obtain two phase mixture of supersaturated α-Fe(Si,B) solid solution. The volume fraction of amorphous phase depends on the milling time. In the case of milling crystalline materials (mixture of crystalline powders or crystallized ribbon), continuous refinement of the microstructure was observed. Dissolution of Si and B atoms in Fe lattice during mechanical alloying of elemental powders occurred simultaneously with crystallite size reduction. The grain size reduction to the nanometer range is accompanied by an increase in atomic-level strain. Decreasing of grain size and increasing of the atomic-level strain lead to the decomposition of the Fe 2 B compound during the milling of the crystallized ribbon. Boron atoms dissolve in the Fe crystalline lattice forming supersaturated α-Fe(Si,B) solid solution. Similar effect was observed during prolonged milling of mechanically crystallized ribbon. All the alloys studied are ferromagnetic with Curie temperatures exceeding 850 K independent of a starting materials. The magnetic moments are reduced with increasing milling time. A multiphase composition is also confirmed by Mossbauer spectroscopy.

Samples of the Fe80Ni20 alloys were synthesized in the low energy conventional horizontal and high energy planetary ball mills. Both in the low and high energy processes, the solid bcc Fe(Ni) solutions with a similar structure are formed. The lattice constants are slightly larger than for the pure iron. Thermal stability of alloys was measured upto 1100 K. The magnetization and ferromagnetic Curie temperatures confirm a ferromagnetic ordering. The magnetic moment equal to 2.07 μB for the longest milling periods proves that the electronic structure of the crystalline alloy with nanometer-sized grains does not differ from that of polycrystalline samples. The distributions of the hyperfine magnetic fields revealed that an iron atom has one to two Ni atoms in the nearest neighborhood.