M. Budzyński

Surface morphology and local magnetic properties of electrodeposited thin iron layers

Thin iron layers with different thickness were prepared by electrodeposition on the polycrystalline substrate. The surface morphology of the layers, their structure and local magnetic properties were studied using scanning tunneling microscopy (STM), X-ray diffraction (XRD) and conversion electron Mossbauer spectroscopy (CEMS). STM studies revealed the granular structure of the surface of the electrodeposited iron layers with the roughness up to 10 nm. XRD analysis proved that these layers were highly strained. The CEMS spectra showed an in-plane magnetic anisotropy in the iron layers. Isomer shift of the electrodeposited iron was different than that of the α-Fe. This difference was attributed to the internal stresses existing in the electrodeposited layers.

Structure and hyperfine interactions in mechanosynthesized iron–molybdenum alloys

Abstract X-ray diffraction and Mossbauer spectroscopy were used to study the structure and hyperfine interactions in Fe 80 Mo 20 and Fe 50 Mo 50 prepared by mechanical alloying. Two solid solutions, i.e. Fe(Mo) and Mo(Fe) with b.c.c. lattice were formed during milling of Fe 80 Mo 20 . Mossbauer spectra revealed different magnetic arrangements in these solid solutions. In the case of Fe 50 Mo 50 no amorphisation was observed, as literature data suggest. During mechanosynthesis of Fe 50 Mo 50 a paramagnetic Mo(Fe) solid solution was probably formed.

Influence of annealing temperature on structural and magnetic properties of MnFe2O4 nanoparticles

Abstract Nanoparticles of manganese ferrite were obtained by the impregnation of highly ordered mesoporous MCM-41 silica support. The investigated sample contained 20% wt. Fe. The obtained nanocrystallites were strongly dispersed in silica matrix and their size was about 2 nm. The sample annealing at 500°C led to increase of particle size to about 5 nm. The Mössbauer spectroscopy investigations performed at room temperature show on occurrence of MnFe2O4 nanoparticle in superparamagnetic state for the sample annealed in all temperatures. The coexistence of superparamagnetic and ferromagnetic phase was observed at liquid nitrogen temperature. The sample annealed at 400°C and 500°C has bigger manganese ferrite particle and better crystallized structure. One can assign them the discrete hyperfine magnetic field components.

Synthesis and characterization of iron oxide magnetic nanoparticles

Abstract Small particles of magnetite, i.e. 7.5, 13.4 and 14.1 nm in diameter, were obtained by the method of co-precipitation. The crystal structure and size distributions were determined by means of transmission electron microscopy and X-ray diffraction. The magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy within the temperature range from 3 K to room temperature (RT). The Mössbauer study of magnetic nanoparticles reveals relaxation behaviour related to the existence of the superparamagnetic phase. The blocking temperature depends on the sizes of the nanoparticles and the ammonia concentration.

Influence of the local environment on the hyperfine interactions in Zr(Fe1-xCox)2 compounds

Ferromagnetic Laves phase compounds Zr(Fe1-xCox)2 have been investigated by means of the Mössbauer effect (57Fe) and by the time-dependent perturbed angular correlation of \gamma -rays (181Ta) technique. It has been concluded from ME experiments that by exchange of Fe by Co in the nearest neighbour shell of the nuclear probe the hyperfine magnetic field acting on 57Fe decreases by 10--12 kG.The analysis of the TDPAC experiments revealed that two different hyperfine magnetic fields: B1hf(Ta)~ 61 kG and B2hf(Ta)~ 88 kG act on the 181Ta nuclei. Both have a negative sign.

The influence of the local surrounding on the hyperfine interactions in Zr(Fe1−xNix)2 compounds

Mössbauer spectroscopy and the TDPAC method have been used to study Zr(Fe1−xNix)2 compounds forx⩽0.30. The hyperfine magnetic field at the Fe sites and the quadrupole splitting as functions of nickel concentration were analysed by use of57Fe Mössbauer spectroscopy. Values of the internal magnetic field on181Ta nuclei have been found by means of the TDPAC method.

Investigation of magnetite Fe3O4 nanoparticles for magnetic hyperthermia

Abstract The paper presents the investigation of magnetic nanoparticles (MNPs) dedicated to hyperthermia application. The crystal structure and size distributions have been determined by means of transmission electron microscope (TEM) and X-ray diffraction (XRD). Magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy together with calorimetric experiments. The Mössbauer spectroscopic study of MNPs revealed the existence of a superparamagnetic phase. The relative contribution of the relaxing component to the total spectrum at room temperature was about 10%. The heating effect of these MNPs under alternating magnetic field was examined. The temperature increase has reached 5°C in 10 min. The preliminary temperature rise suggests that the investigated materials are applicable for hyperthermia.

Hyperfine field assessment of the magnetic structure of ZrZn2

Time differential perturbed angular gamma-gamma-correlation (TDPAC) method on 111Cd nuclei probes inserted in ZrZn1.9 is used to measure the magnetic hyperfine fields (MHF) at Zr and Zn sites and the electric field gradient (EFG) Vzz at Zn sites as a function of temperature at various pressures and as a function of pressure at the temperature 4 K. Our data indicate that the local magnetic moment of Zr in the magnetically ordered state is substantially larger than its value obtained from the macroscopic measurements and that there is also an induced magnetic moment at the Zn site. We conclude that ZrZn2 is not a simple ferromagnet and discuss a possible type of its magnetic ordering.

Mössbauer study of treated Nd2Fe14B

Abstract The Nd2Fe14B cylindrical magnets were treated with water solutions of alkali, acid, and salt. Mössbauer spectroscopy was applied to study the composition and properties of the surface material of the treated magnets. It is shown that the main phase of the permanent Nd2Fe14B magnet partly decomposes. The released α-Nd at the grain boundaries interacts with water and forms neodymium hydroxide matrix, and the released Fe diffuses into it. The presence of Fe-Nd(OH)3 is reflected in the paramagnet doublet in the Mössbauer spectra of treated neodymium magnets.

Hyperfine magnetic fields at rare-earth elements in ferromagnetic transition metals

Hyperfine magnetic fields for such probes as:152SmFe,152SmCo,152SmNi,155GdFe,172YbFe,172YbCo and172YbNi have been measured using PAC method. The quantitative analysis of components of these fields has been also performed.