Emergence of order in nanocrystalline SmFe9

Journal of Applied Physics

2010

The structure and magnetic properties of nanocrystalline PrCo3 prepared by high-energy milling technique have been investigated by means of X-ray diffraction using the Rietveld method coupled to Curie temperature and magnetic measurements. The as-milled samples were subsequently annealed in temperature range from 750 to 1050• C for 30 min to optimize the extrinsic properties. From x-ray studies of magnetic aligned samples, the magnetic anisotropy of this compounds is found uniaxial. The Curie temperature is 349 K and no saturation reached at room temperature for applied field of 90 kOe. The coercive field of 55 kOe and 12 kOe measured at 10 and 293 K respectively is obtained after annealing at 750• C for 30 min suggests that nanocrystalline PrCo3 are interesting candidates in the field of permanent magnets. We have completed this experimental study by simulations in the micromagnetic framework in order to get a qualitative picture of the microstructure effect on the macroscopic magnetization curve. From this simple model calculation, we can suggest that the after annealing the system behaves as magnetically hard crystallites embedded in a weakly magnetized amorphous matrix.

Section: Methodsmentioning

confidence: 99%

Structure and magnetic properties of nanocrystalline PrCo3

Younsi

Russier

Journal of Applied Physics

2010

“…According to our previous results on the nanocrystalline precursors of SmFe 11 Ti [6] and Sm 2 Fe 17 [7], we have prepared out-of-equilibrium R Fe 9 x -Co x Ti (x = 0.5, 1, 1.5, 2, R = Pr, Sm) and SmFe 9 y y M -(y = 0.25, 0.5, 0.75, 1, M = Si, Ga) alloys by ball-milling, under high purity Ar atmosphere, inductively melted pre-alloys with composition checked by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The resulting powders were subsequently annealed under 10 6 -Torr at temperature 700 -750 °C for 30 min; after annealing, the overall chemical composition of all samples was controlled by (ICP-AES) and appeared within the experimental uncertainties (± 0.04) in agreement with the nominal composition.…”

Section: Methodsmentioning

confidence: 97%

“…Both precursors are relevant of the 6 P mmm / spacegroup and generally known as TbCu 7 , derived from CaCu 5 [3 -5] while equilibrium structure 3 R m and 4 I mmm / constitute super-lattices of the hexagonal sub-cell. However, we have recently demonstrated by Rietveld analysis coupled to Mössbauer spectroscopy that the precursor of Sm(Fe, Ti) 12 is Sm(Fe, Ti) 10 [6] and SmFe 9 is the precursor of Sm 2 Fe 17 [7].…”

Section: Introductionmentioning

confidence: 99%

Out‐of‐equilibrium nanocrystalline R_1–s(Fe, M)_5+2s alloys (R = Sm, Pr; M = Co, Si, Ga)

Physica Status Solidi (b)

Djéga‐Mariadassou

2005

The out-of-equilibrium hexagonal 6 P mmm / 1 s R -(Fe, M) 5 2s + (R = Sm, Pr and M = Co, Si or Ga) intermetallics are obtained by controlled nanocrystallization. A model is presented to explain the structure of the hexagonal phases, which stoichiometry is consistent with Sm(Fe, M) 9 and R(Fe, Ti, Co) 10 . The Curie temperatures increase versus Ga, Si, Co content. The analysis of the Mössbauer spectra leads to monotonous variation of the hyperfine parameters. The refinement of the Mössbauer spectra was performed on the basis of the correlation between Wigner -Seitz cell volumes obtained from X-ray diffraction results and isomer shifts. The abundance of each magnetic site was calculated by the multinomial distribution law. For a given substituting Co, Si, Ga content, the sequence for the isomer shift in the hexagonal cell is 2 3 6 e g l > > . With increasing M content, the isomer shift of the 3g site remains quasi-constant. Those approaches lead to the location of Si, Ga, Co in 3g site, Ti in 6l site.

“…Samples SmFe 9−x Co x Ti (x = 0.5, 1, 1.5, 2) and SmFe 9−y M y (y = 0.25, 0.5, 0.75, 1 M=Si,Ga) were prepared by high energy ball milling technique with appropriate mix of Sm 2 Fe 17 prealloy and balanced Ti, Co, Si, Ga powders followed by subsequent annealing between 600 • C and 850 • C as described previously [8,9].Carbonation was achieved after reacting the powders ground to 30 μm with an appropriate amount of C 14 H 10 powders at 420 • C.…”

Section: Methodsmentioning

confidence: 99%

“…Both precursors are commonly described as relevant of the same TbCu 7 description of the P6/mmm space-group derived from CaCu 5 [3,6,7] although the subsequent equilibrium phases do not correspond to the same stoichiometry. In fact, we have demonstrated that the precursor of Sm 2 Fe 17 is SmFe 9 [8] and R(Fe,Ti) 10 for R(Fe,Ti) 12 (R=Sm,Pr) [9,10].…”

mentioning

confidence: 94%

Out-of-equilibrium Sm–Fe based phases

Djéga‐Mariadassou

2008

Hyperfine Interact

Structure and magnetic properties of nanocrystalline P6/mmm out-ofequilibrium precursors of hard magnetic R-3m Sm 2 (Fe,M) 17 C (M=Ga,Si,) and I4/mmm Sm(Fe,Co,Ti) 11 equilibrium phases, are presented. Their structure is explained with a model ground on the R 1−s T 5+2s formula (R=rare-earth, s=vacancy rate, T=transition metal) where s Sm atoms are statistically substituted by s transition metal pairs. The Rietveld analysis (RA) provides the stoichiometry of the precursors, 1:9 and 1:10, respectively precursor of 2:17 and 1:12 phases. The interpretation of the Mössbauer spectra of the 1:9 and 1:10 phases, is based on the correlation between δ and the Wigner-Seitz Cell volumes, calculated from the structural parameters. The δ behaviour of each crystallographic site versus Co content, defines the Co location while it confirms that of Si and Ga obtained by RA. Substitution occurs in 3 g site, whatever Co or M. The Sm(Fe,Co,Ti) 10 and Sm(Fe,M) 9 C Curie temperature (T c ) are compared to those of the equilibrium phases, the effects of Fe substitution and C addition are discussed. The maximum μ 0 H c is obtained for low M or Co content, for auto-coherent diffraction domain size ∼30 nm. SmFe 8.75 Ga 0.25 C and SmFe 8.75 Si 0.25 C with T c of 680 and 690 K, show respectively M r and μ 0 H c of 58 emu/g, 27 kOe and 95 emu/g, 15 kOe, values higher than those obtained for Sm 2 (Fe,M) 17 carbides.