Andrzej Bombik

Solid solutions TbFe1−xAlxO3 (0 ⩽ x ⩽ 1): Structure and magnetic behaviour☆

Abstract Magnetic X-ray, neutron diffraction and DSC measurements for a solid solution of the TbFe 1− x Al x O 3 system have been carried out. The results obtained indicate an essential role for Al substitutions on the magnetic behaviour of the compounds examined. For low Al concentration, a radical reduction of magnetic susceptibility of the compounds has been observed. The increase in Al concentration ( x = 0.4−0.7) generates a compensation temperature (∼35 K) in the system. This effect is responsible for the change in the type of Tb-Fe coupling (from ferromagnetic to antiferromagnetic).

Magnetic susceptibility of powder and single-crystal TmFeO3 orthoferrite

Abstract This paper presents the results of magnetic susceptibility investigations carried out on TmFeO 3 samples, both single crystal and powder. It is shown that powder specimens exhibit a pronounced magnetic thermoremanence effect. This effect can be employed to determine phase transition temperatures from susceptibility measurements performed on polycrystalline substances. Until now, these temperatures had been obtained only from examining the spontaneous magnetisation of single-crystal specimens. The spin reorientation temperatures obtained from various measurements are compared.

Magnetic behaviour of TmFe1−xAlxO3 system (x≤0.1)

Magnetisation measurements for some representatives of TmFe 1−x Al x O 3 system were performed. Singularities on the experimental curves mark some phase transition points of the investigated substances. The obtained results indicate an essential influence of Al substitution on magnetic behaviour of examined compounds: a rise in T c and T t1 , T t2 , compensation and spin reorientation process temperatures respectively, as well as broadening of the temperature range of reorientation process

AC susceptibility of TmFeO3 single-crystal

Abstract This paper presents the results of AC-susceptibility measurements performed on TmFeO 3 single-crystal orthoferrite. The AC-measurements were carried out without any static magnetic field ( H 0 =0) but for different frequencies and amplitudes of the oscillating field. It is shown that singularities of both (in-phase and out-of-phase) AC-susceptibility components closely correlate with phase transitions in TmFeO 3 . From the dynamic susceptibility temperature dependence some information about magnetic domain and system non-linearity can be derived.

Magnetic structures of RNi2Ge2 (R = Dy, Ho and Er) and YbNi2Si2

Abstract Results of X-ray, neutron diffraction, Mossbauer effect and magnetometric measurements for RNi 2 Ge 2 (R = Dy, Ho and Er) and YbNi 2 Si 2 compounds are presented. All compounds crystallize in the tetragonal ThCr 2 Si 2 (CeAl 2 Ga 2 )-type crystal structure and are antiferromagnets with the Neel temperature of 7.5 K for R = Dy, 4.8 K for R = Ho and 3.65 K for R = Er and 2.3 K for YbNi 2 Si 2 . Below T N a sinemodulated structure with k = (0, 0, k z ) is observed for RNi 2 Ge 2 compounds (R = Dy and Er) and with k = ( k x , k y , k z ) for HoNi 2 Ge 2 . The YbNi 2 Si 2 has a helicoidal ordering confirmed by the Mossbauer effect data. The Ni atom is non-magnetic and rare earth moments form an angle φ with the c -axis which changes from 20° for R = Dy to 90° for YbNi 2 Si 2 . The obtained data are analyzed in terms of the RKKY theory and crystal electric field.

Magnetic susceptibility of LaxCe1−xF3 single crystals

Abstract The ac susceptibility of LaxNd1−xF3 single crystals, for 0 ≤ x ≤ 0.1, has been measured from 1.5 up to 40 K and their dc susceptibility for 0 ≤ x ≤ 1 has been measured from 3 up to 300 K in magnetic fields up to 0.2 T. In both susceptibilities the magnetic fields were applied parallel to the crystallographic a-axis (perpendicular to the c-axis). The effective Bohr magneton number Peff and paramagnetic Curie temperature θp have been obtained, using the Curie-Weiss law in the temperature range 100–300 K. Also the g-values corresponding to the five Kramers doublets in the 4I9/2 ground multiplet of Nd3+ ion in LaxNd1−xF3 have been determined in the direction perpendicular to the c-axis, using the Van Vleck theory of paramagnetic susceptibility. The effect of the dilution of the paramagnetic Nd3+ ions with diamagnetic La3+ ions is also discussed.

AC and DC susceptibility of powder solid solutions of TmFe1-xAlxO3 and TmFe1-xGaxO3 systems (x≤0.15)

Abstract The paper presents the results of static and AC susceptibility measurements for powder solid solutions of two systems: TmFe 1− x Al x O 3 and TmFe 1− x Ga x O 3 . The magneto-thermoremanence effect occurring in these systems is explained, and it is shown as to how this effect can be used to determine phase transition temperatures in powder compounds. It has been found that spin reorientation temperatures are dependent on the concentration of non-magnetic atoms in the iron sublattice, and that the compensation temperature is dependent on the type of non-magnetic atoms. Also, it has been found that the non-magnetic atoms have a strong dampening effect on the intensity of higher harmonic components of AC susceptibility.

New magnetic properties of (Co1-xMnx)2P

Abstract Atmospheric and high-pressure susceptibility measurements of (Co1−xMnx)2P samples with x = 0.6 and 0.75 are presented. The second composition shows evidence of a new zero-pressure magnetic phase transition. The magnetvolume effect based on χac susceptibility/pressure measurements is discussed in the framework of localized/delocalized models.

Exchange interactions in the helimagnetic spinel solid solutions Zn1−xGa2x3Cr2Se4 (where 0.0≤x≤0.5)☆

Abstract Magnetic phase transition from the magnetic simple spiral state (for x = 0.0) to the spin glass state (for x = 0.5) results from the high degree of frustration of exchange interactions in the chromium spinel sublattice. Using experimental values of: the Curie-Weiss paramagnetic temperature, the Neel temperature and the rotation angle of the spiral, the exchange parameters are estimated (using a mean-field theory) up to the third coordination sphere for the whole range of concentration.