Z. Smetana

Magnetic structures and related properties of some rare-earth intermetallic compounds, RCu2

Abstract The magnetic structures and some relevant bulk magnetic properties of R(Cu, Ni) 2 (R = Tb, Tb z Y 1− z , Dy, Ho, Er and Tm) are summarized. Basically, the magnetic structures are antiferromagnetically modulated with propagation vector 1 3 a ∗ . For R = Tb, Dy, Ho the a -axis anisotropy dominates and the structures are longitudinally modulated. For R = Tm, Er (probably) the b -axis anisotropy dominates and this results in transversely modulated structures. For R = Tb, Dy the structures are collinear, For R = Ho, Er, Tm (probably) an incommensurate modulation coexists with the commensurate a ∗ -axis modulation at the lowest temperature.

The effect of local disorder on the magnetic, electric and thermal properties of RE(Fe1-xAlx)2 (RE=Gd, Dy)

Measurements of magnetic properties, X-ray and neutron diffraction, differential thermal analysis (DTA), thermal expansion and resistivity were made on Gd(Fe1-xAlx)2 and Dy(Fe1-xAlx)2. Both systems exhibit a line broadening observed by X-ray diffraction on the Al-rich side, indicating a small variation of the lattice constants. This effect leads to a smoothing of the magnetic phase transition at the Curie temperature Tc, which becomes observable in all the measurements mentioned above. The neutron experiments give evidence of a disordered component of the Dy moment due to Fe substitution. By subtracting the thermal expansion of non-magnetic YAl2 from that of the mixed crystal series, a reduction of the spontaneous magnetostriction from its value in the corresponding boundary phase is also obtained. In the case of anisotropic Dy the magnetisation behaviour can be explained by the pinning of narrow domain walls on inhomogeneities caused by chemical substitution. All physical properties indicate a magnetically quasi-amorphous state.

Neutron diffraction study of the magnetic structure of HoCu2

Abstract Neutron diffraction measurements show that in the temperature range from 7.4 to TN=10.4 K the magnetic structure of HoCu2 is a commensurably modulated a-axis collinear structure with a wave vector q1=1/3a∗. Below 7.4 K an additional structure component develops and the low temperature magnetic structure of HoCu2 is found to be an incommensurably modulated non-collinear structure characterized by wave vectors q1=/13;a∗, q2=qcc∗ and 2q2, where a∗ and c∗ are reciprocal lattice vectors of the orthorhombic structure and qc=0.300±0.005. The corresponding moment components μ-q1, μq2 and μ2q2 lie along the a, b and b directions of the orthorhombic crystal lattice, respectively.

Magnetic arrangement in the Dy(Fe1−xAlx)2 pseudobinary laves phases

Abstract The magnetic structure and magnetic moments of Dy and Fe have been studied at 4.2 K by means of neutron diffraction measurements on powdered samples of Dy(Fe 1− x Al x ) 2 for x=1.0, 0.9, 0.3 (the C 15 structure) and for x=0.5 (the C 14 structure). A strong reduction of the Dy-moment for x≤0.9 is explained by the crystallographic disorder in the Fe-Al sublattice as well as lattice defects.

Temperature dependence of the magnetic structure of TbCu2

Abstract The orthorhombic compound TbCu 2 was studied by neutron powder diffraction. The temperature development of the magnetic structure is interpreted by means of Fourier analysis of the diffraction data below T N = 55 K .

Neutron diffraction study of the R(Cu1-xNix)2(R = Tb, Ho) system

Abstract Neutron diffraction study on powder samples of Tb(Cu1-xNix)2 with x = 0.00, 0.05, 0.10 and Ho(Cu1-xNix)2 with x = 0.00, 0.10 was performed at T = 4.2, 2.5K and above ordering temperature. In both cases (R = Tb, Ho) for x = 0.10 the decreasing concentration of conduction electrons gives rise to predominate ferromagnetic component.

On crystal-field spectroscopy based on specific heat and thermal expansion measurements: application to the TmCu2 intermetallic compound

An experimental study based on specific heat, thermal expansion, magnetisation and neutron diffraction measurements on polycrystal and single crystal of the orthorhombic TmCu2 compound is presented. The results are satisfactorily interpreted within a model involving the crystal and molecular field acting on the Tm3+ ions. The energy spectrum of the ground-state multiple 3H6 of Tm3+ with the isolated split lowest quasi-doublet ( Delta 1=5+or-1 K, Delta 2=68+or-3 K) is proposed. The appropriate sets of crystal-field parameters Vlm are obtained and discussed.

On the temperature dependence of the sublattice magnetizations in TbCu2

Abstract Calculations based on molecular and crystal field models were used for the interpretation of the temperature dependence of the sublattice magnetizations found by neutron diffraction in the antiferromagnetic compound TbCu 2 . The observed dependence is explained as a result of comparable amounts of exchange and crystal field energy in this compound.

Low temperature magneto-optical studies of NiPt multilayers

Abstract Magneto-optical (MO) polar Kerr effect spectra in Ni Pt multilayers at 80 K show a strong increase in the spectra amplitudes, which exceeds that predicted by the model based on electromagnetic theory. An enhancement of the Kerr effect is observed at photon energies above 3 eV, similar to that in Co Pt and Fe Pt .

Magneto-optical enhancement in Pt/(Ni1−xCox) multilayers

Abstract Magneto-optical (MO) polar Kerr rotation (PKR) and ellipticity (PKE) spectra of Pt/(Ni 1− x ) multilayers with x = O, 0.3 and 1 nm prepared by evaporation under ultrahigh-vacuum conditions were studied. The thickness of the Pt layer was kept between 1.5 and 2 nm, and that of the ({Ni 1− x Co x }) alloy layer, t Ni 1− x Co x , was 0.45 and 1.4 nm Layers formed at the Pt—magnetic layer interfaces give rise to a surface-induced perpendicular magnetic anisotropy (PMA) and to an enhancement of PKR in the near-UV spectral region. Because the Curie temperature T c is close to 300 K for x = O a clear manifestation of these effects in the Ni/Pt system required cooling to low temperatures. The possibility to optimize the characteristics, like PMA, T C and the amplitude and position of the PKR peak in the spectra by proper choices of x , t Pt and t Pt and t Ni 1− x Co x makes Pt/(Ni 1− x Co x ) multilayers interesting for the realization of MO storage media capable of working in blue light.