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The results of X-ray diffraction, magnetic susceptibility and Mossbauer investigations of RFe 10 Cr 2 intermetallic compounds (R=Y, Nd, Gd, Tb, Dy, Ho, Er and Tm) are presented and discussed. The variation with a sample composition of the lattice constants, unit cell volume, Curie temperature, iron and rare earth magnetic moments, magnetic anisotropy field and 57 Fe hyperfine interaction parameters are shown. The Curie temperatures of the RFe 10 Cr 2 series follow the same trend as in other R-Fe compounds and range from 466 K (for TmFe 10 Cr 2 ) to 585 K (for GdFe 10 Cr 2 ). Spin reorientation transition phenomena caused by the competition between the rare earth and iron sublattice magnetic anisotropies are observed for R=Tb, Dy and Er. The sample composition has little influence on the 57 Fe hyperfine interaction parameters. The numerical analysis of Mossbauer spectra shows that chromium atoms have a pronounced preference for occupying 8i sublattice in the whole series of the investigated compounds. From the magnetic susceptibility and Mossbauer data the approximate values of iron and rare earth magnetic moments are derived.

The magnetization variation with a temperature of Y/sub x/Fe/sub 80-x/B/sub 20/ and Y/sub x/Co/sub 70-x/B/sub 30/ amorphous ribbons has been investigated. For an accurate description of the low temperature behaviour of magnetic properties the spin wave theory has been used. The value of the spin wave stiffness constant, D, was calculated for all investigated samples. For the ferromagnetic Y-Co-B alloys D is a linear function of Curie temperature, T/sub C/. An analogous relation for asperomagnetic Y-Fe-B ribbons was not found. >

The influence of Y and Pr on the magnetic properties of amorphous Y x Fe 80- x B 20 ( x = 0, 2, 4, 6 and 8) and Pr x Fe 80- x B 20 ( x = 2, 4 and 6) was investigated by Mossbauer spectroscopy and by magnetic measurements. It was found that the averaged value of 57 Fe hyperfine magnetic field, the value of the saturation magnetization and the Curie temperature decrease with the increase in Y or Pr content.

The radio-frequency (rf) collapse of the magnetic hyperfine structure in the Mossbauer spectra is employed to study changes in the short-range order in amorphous metals via the electric quadropole hyperfine interaction. The structural changes in amorphous Fe 80- x R x B 20 (where R = Y, Sm, Pr) alloys were studied in detail as a function of x . It was found that such substitutions induce considerable changes in the short-range order. A low concentration of substituting atoms ( x x >4) lead to collective changes in the structure.

The influence of the partial substitution of iron by copper or chromium on the crystal and magnetic properties of Y2Fe14B has been investigated with X-ray diffraction, magnetometric and Mossbauer effect methods. The substitution of iron by chromium results in the linear decrease in both the a and c lattice constants. The opposite effect is observed when iron is replaced by copper. The Curie temperature decreases when iron is substituted by chromium but it increases when copper replaces iron. The substitution process leads to a decrease in saturation magnetization of both series of compounds. In contrast to copper, the substitution of chromium for iron has a great influence on the 57Fe hyperfine magnetic fields which cannot be accounted for by the random distribution of the substituent atoms among iron crystal sites.

The resistivity and magnetoresistance of RxCo70-xB30 and RxFe80-xB20 (R = Y, Pr, Sm, Tb, Dy, Ho, Er, Tm; 0 ≤ x ≤ 8) amorphous alloys are investigated. The transverse magnetoresistance increases with growth of x in all investigated ribbons and the temperature resistivity coefficient becomes negative. The positive slope of the magnetoresistance in all ribbons with Co and for some ribbons with Fe is caused by the magnetic structure of the investigated alloys and by the band effects.

The value of the saturation magnetostriction, λs, SmxFe80−xB20 at room temperature decreases from 37×10-6 for x=1 to 12×10-6 for x=9. The relation between the value of λs, and topological short-range order (SRO) in terms of the two-ion model of magnetostriction is discussed. The position of two neighbouring radial distribution function maxima points out that the first coordinating zone is composed of two sub-zones. The number and distances between the nearest neighbours Sm-Fe and Fe-Fe in the ribbons are analogous to the local symmetry in the SmFe2 crystalline phase with a very large magnetostriction of −1560×10-6.

Radio-frequency (rf) collapse of the magnetic hyperfine structure in the Mossbauer spectra is employed to study directly the changes in the short range order in amorphous Fe80−xLaxB20 alloys via the electric quadruple hyperfine interaction. Substitution of iron by the much larger La atoms induced collective changes in the structure.

The spin reorientation transitions were investigated in ErFe 10 T 2 where T = Cr , Si . The initial susceptibility of these compounds was measured in the temperature range from 4.2 to 77 K. The spin reorientation temperature, T SR , is found to be about 25 K in ErFe 10 Cr 2 and 48 K in ErFe 10 Si 2 . The results are discussed applying the crystal field (CEF) model. The 4th and 6th crystal field terms, when having appropriate positive values, explain SR in these compounds.

The magnetic properties (Curie temperature and spin reorientation) have been investigated. The Curie points as well as spin reorientation temperature decrease when Fe is substituted by Cr. The decrease of the Curie temperature is explained by the molecular field model. The change of the spin reorientation temperatures with increasing Cr concentration is discussed in the combined crystal field-exchange field model.

The results of magnetic measurements performed on Y 2 Fe 14−x M x B compounds, where M = Si, Cr and Cu, are reported. The saturation magnetization at 4.2 K decreases with increasing of an M element. The rate of the decrease is larger than that expected by a simple dilution model. The influence of M atoms on the anisotropy is discussed.

Magnetic properties (saturation magnetization at 4.2 K, Curie temperature and spin reorientation temperature) of Nd2Fe14-xMxB systems (M = Si, Cr and Cu) are investigated. These compounds crystallize in a tetragonal Nd2Fe14B structure. Based on these measurements, the temperature-composition diagrams of spin arrangements appearing in Nd2Fe14-xMxB systems have been established.

The spin reorientation transitions are investigated in RFe10T2 where R = Tb, Dy, Ho and T = Cr, Si. The initial susceptibility of these compounds was measured in the temperature range from 77 K to room temperature. The spin reorientation temperature, TSR, is found to be about 190 K in DyFe10Cr2 and 298 K in TbFe10Cr2. In DyFe10Si2TSR = K. The res are discussed applying the crystal field model.

The results of magnetic and structural measurements performed on the Nd 2 Fe 14- x Nb x B and Nd 2 Fe 12- x Nb x Co 2 B compounds with 0 ⪅ x ⪅ 0.5 are presented. All the compounds studied crystallize in the tetragonal Nd 2 Fe 14 B structure. The saturation moments decrease by introducing Nb. The rate of the decrease is larger than that expected by a simple dilution model. The Curie temperatures and anisotropy fields are found to increase. Thus a small amount of Nb incorporated into Nd 2 Fe 12 Co 2 B may benefit this material for permanent magnet fabrication.

The structural and magnetic properties of RFe 10 Si 2 , R=Y, Gd, Tb, Dy, Ho, Er, Tm, are investigated. X-ray diffraction shows that these materials crystallize in the tetragonal ThMn 12 structure. The Curie temperatures vary in the range from 535 to 613 K. Saturation magnetization at 77 and 295 K and the anisotropy field at 295 K are determined. The spin-reorientation phase transitions are investigated in the range from 77 K to room temperature. The mean field approximation was applied to establish intra- (Fe-Fe) and intersublattice (R-Fe) exchange interactions. The properties of these compounds are compared with those of R 2 Fe 14 B alloys.

The structure and magnetic properties of RFe 10 Cr 2 compounds where R = Y, Nd, Gd, Tb, Dy, Ho, Er, Tm are investigated. X-ray analysis reveals that RFe 10 Cr 2 alloys are of the tetragonal ThMn 12 structure. The lattice constants, Curie temperature, saturation magnetization at 77 and 295 K and the anisotropy field at 295 K are determined. The mean-field approximation is applied to obtain the R-Fe coupling constant. The properties of these compounds are compared with those of R 2 Fe 14 B alloys.

The transverse magnetoresistance of Ho x Co 70- x B 30 amorphous ribbons in the composition range 0⪕ x ⪕8 was measured in pulsed magnetic fields up to 22 T. A positive contribution to the magnetoresistance was found in all investigated alloys. The results are interpreted in terms of the band model of magnetism and antiferromagnetic RE-3d exchange interactions.

The Sm 2 (Co 1-x Ag x ) 17 alloys in the concentration range 0 \leq x \leq 0.07 have been studied. The unit cell volume is found to increase by introducing Ag. The saturation magnetization monotonically decreases with x . The anisotropy constant K 1 at room temperature increases from 3.2J/cm3for Sm 2 Co 17 to 6.2 J/cm3for Sm 2 (Co 0.97 Ag 0.03 ) 17 . A small amount of Ag incorporated to Sm 2 Co 17 significantly beneficiates this material for permanent magnets fabrication.

Structural and magnetic characteristics of R2Fe14-xCuxB systems (R = Y, Nd and Gd) have been investigated. These compounds crystallize in a tetragonal system of P42/mnm-type for a Cu content up to x⩽1.5. The Curie temperature and lattice parameters a and c increase with substitution of Fe by Cu. The spin-reorientation temperature in the Nd2Fe14B compound is lowered when Cu replaces Fe. The effects of Fe substitution by Cu on the saturation magnetization and the anisotropy field are presented.

The influence of chromium on the electrical resistivity minimum and on the magnetoresistance of amorphous Fe 40-x Ni 40 Cr x B 20 ribbons have been investigated in the compositional range 0 ≤ × ≤ 14. The position of the resistivity minimum is shifted to higher temperatures with increasing chromium content, from 21 K for x=0 to 215 K for x=14. In high magnetic fields an admixture of chromium changes the sign of the magnetoresistance. The results have been qualitatively interpreted in the effective internal field distribution.