Magnetocaloric Properties of Fe 75 Mo 8 Cu 1 B 16 and Fe 81 Mo 8 Cu 1 B 10 Metallic Glasses

Phys. Chem. Chem. Phys.

Pavlovič

Procházka

et al. 2015

Evolution of structure and local magnetic fields in (Fe1-xCox)76Mo8Cu1B15 (HITPERM) metallic glass ribbons with various amounts of Co (x = 0, 0.25, 0.5) were studied in situ using diffraction and nuclear forward scattering of synchrotron radiation. It was found that crystallization for all three glasses proceeds in two stages. In the first stage, bcc (Fe,Co) nanocrystals are formed, while in the second stage additional crystalline phases evolve. For all three glasses, the crystallization temperatures at the wheel side were found to be lower than at the air side of the ribbon. The crystallization temperatures were found to decrease with increasing Co content. The lattice parameters of the bcc nanocrystals decrease up to about 550 °C and then increase pointing to squeezing Mo atoms out of the nanograins or to interface effects between the nanocrystals and the glassy matrix. Nuclear forward scattering enabled separate evaluation of the contributions that stem from structurally different regions within the investigated samples including the newly formed nanocrystals and the residual amorphous matrix. Even minor Co content (x = 0.25) has a substantial effect not only upon the magnetic behaviour of the alloy but also upon its structure. Making use of hyperfine magnetic fields, it was possible to unveil structurally diverse positions of Fe atoms that reside in a nanocrystalline lattice with different number of Co nearest neighbours.

Section: Resultsmentioning

confidence: 94%

Evolution of structure and local magnetic fields during crystallization of HITPERM glassy alloys studied by in situ diffraction and nuclear forward scattering of synchrotron radiation

Phys. Chem. Chem. Phys.

Pavlovič

Procházka

et al. 2015

“…CEMS spectrum in Figure 1(a) suggests that the investigated system has close-to-room Curie temperature in the as-quenched state. Indeed, in our recent work we have determined = 313 K [32] for this MG using temperature dependence of magnetization.…”

Section: Resultsmentioning

confidence: 99%

“…The 1/ curves ( = 0.36) were fitted with linear lines which have provided = 316 K for all irradiated samples. A small increase of after ion irradiation is observed in comparison to the nonirradiated as-quenched alloy ( = 313 K [32]). Nevertheless, the observed change falls nearly into the error range.…”

Section: Ion Irradiationmentioning

confidence: 90%

Impact of Ion Irradiation upon Structure and Magnetic Properties of NANOPERM‐Type Amorphous and Nanocrystalline Alloys

Journal of Nanomaterials

Hasiak

2015

Structural modifications and their impact upon magnetic properties are studied in amorphous and nanocrystalline NANOPERM-type57Fe75Mo8Cu1B16alloy. They are introduced by irradiation with 130 keV N+ions to the total fluencies of up to 2.5 × 1017 ions/cm2under different cooling conditions. Increased temperature during the irradiation triggers formation of nanocrystallites of bcc-Fe in those subsurface regions that are affected by bombarding ions. No crystallization occurs when good thermal contact between the irradiated sample and a sample holder is assured. Instead, structural rearrangement which favours development of magnetically active regions was determined by the local probe methods of Mössbauer spectrometry. Dipole magnetic interactions dominate in subsurface regions on that side of the ribbons which was exposed to ion irradiation. Nevertheless, structural modifications demonstrate themselves also via macroscopic magnetic parameters such as temperature dependence of magnetization, Curie temperature, and hysteresis loops. Impact of only the temperature itself to the observed effects is assessed by the help of samples that were subjected just to heat treatment, that is, without ion irradiation.

“…b. It might be due to moderate temperature increase caused by irradiation which, in turn, causes structural relaxation of the amorphous phase toward non‐magnetic arrangement. These subtle structural modifications are demonstrated through the disappearance of weak magnetic interactions in the as‐quenched alloy.…”

Section: Resultsmentioning

confidence: 99%

Ion irradiation induced structural modifications of Fe₈₁Mo₈Cu₁B₁₀ NANOPERM‐type alloy

Physica Status Solidi (a)

Hasiak

2015

Structural modifications and their impact upon magnetic properties are studied in amorphous NANOPERM‐type 57Fe81Mo10Cu1B10 metallic glass exposed to irradiation with 130 keV N+ ions to the total fluencies of up to 2.5 × 1017 ions/cm2. Using surface sensitive technique of Mössbauer spectrometry, traces of crystalline phases are found already in the as‐quenched state after the sample production. On the air side of the ribbons, bcc‐Fe dominates whereas on the opposite wheel side, also a presence of Fe3O4 is unveiled. The amount of surface crystallization is higher on the wheel side of the ribbons. After ion irradiation, mostly the air side is affected because it was facing the incident ions. Gradual formation of iron nitrides is observed with increasing ion fluence. Though the radiation damage exhibits itself only at this side of the ribbons, its influence upon bulk magnetic properties is clearly identified by the help of magnetic measurements. Hysteresis loops exhibit changes in their shape as well as coercive field. Along with the formation of magnetic crystalline phases (bcc‐Fe and nitrides), they are caused by structural rearrangement which takes place also inside the amorphous residual phase. Structural modifications are confirmed via evolution of hyperfine magnetic fields with ion fluence. Structural modification of the 57Fe81Mo10Cu1B10 alloy caused by ion irradiation as demonstrated by microstructural (Mössbauer spectrometry (a,b)) and macroscopic (hysteresis loops (c,d)) measurements. As‐quenched (a,c) and 2.5 × 1017 N+/cm2 irradiated (b,d) alloys are compared.