Y. Janssen

Magnetic properties of single-crystalline Y2Co15Si2

We have studied the magnetic properties of an Y2Co15Si2 single crystal. The magnetic anisotropy has been analyzed in the temperature range 5-350 K by means of the Sucksmith-Thompson method. Both the first-order anisotropy constant K-1 and the second-order anisotropy constant K-2 are found to be positive, the former being more than an order of magnitude larger than the latter at all temperatures. Measurements of the field dependence of the magnetization made in the easy and hard direction show that there is small but significant anisotropy of the saturation moment

Magnetocrystalline anisotropy of TbFe12-xTix single crystals

TbFe12−xTix single crystals have been investigated by means of magnetic measurements. With decreasing temperature, a spin-reorientation transition from easy axis to easy plane occurs. The rate of decrease of spin-reorientation temperature with x is about −380 K/Ti. There exists a strong magnetocrystalline anisotropy in the basal plane. The anisotropy field Ba between [100] and [110] for the compound TbFe11.15Ti0.85 is as high as 35 T which is about three times Ba in the axial direction. With increasing x, the easy magnetization direction at low temperatures in the basal plane changes from [110] for x=0.85 to [100] for x=1.0. The composition dependence of anisotropy can be understood in terms of a change of the crystal field parameters Anm due to substitution of Ti for Fe.

Antiferromagnetic ordering in the novel Ho3Ge4 and HoGe1.5 compounds studied by neutron diffraction and magnetic measurements

The magnetic ordering of the novel binary compounds ( structure type, space group Cmcm) and ( structure type, space group ) has been studied by neutron diffraction and magnetic measurements. Antiferromagnetic ordering of sets in below . The two Ho sites order independently with two distinct order parameters associated with the same wave vector q = (010). Both sublattices have a uniaxial antiferromagnetic moment arrangement but with mutually perpendicular orientations. In a first step the sublattice orders with a uniaxial moment arrangement along c. In a second step the sublattice orders perpendicular to with a uniaxial arrangement along a. Below the resulting two-dimensional canted antiferro-magnetic structure is described by the monoclinic magnetic space group . At 1.4 K the ordered moment values of and are and , respectively. The magnetic ordering of the coexisting novel phase with the structure type (space group ) has been also studied. The Ho moments order antiferromagnetically below . The collinear moment arrangement is associated with the wave vector and is described by the magnetic space group . At 1.4 K the ordered magnetic moment is confined to the (001) plane.

Magnetic properties of a DyCo10V2 single crystal

Abstract We have studied the magnetic properties of a single crystal of the DyCo 10 V 2 compound. This compound has the tetragonal ThMn 12 structure. The easy magnetization direction is parallel to the c axis at high temperatures. The magnetization tilts away from the c axis below the spin reorientation temperature at T SR =42 K, reaching a value of θ C =27° at 5 K. The magnetic compensation of the Co and Dy sublattice magnetizations leads to a sharp minimum at T COMP =118 K. The shape of the M ( T ) curves is strongly field-dependent and is considerably influenced by the thermal history of the sample. This behaviour is attributed to the development of a rather strong intrinsic coercivity at low temperatures, originating from the presence of narrow Bloch walls. The temperature dependence of the coercivity, diverging at the compensation temperature, was compared with model predictions.

Antiferromagnetic ordering in the novel (two-step) and -type) compounds studied by neutron diffraction and magnetic measurements

The magnetic ordering of the novel binary compound with two Tb sites ( structure type, space group Cmcm) has been studied by neutron diffraction and magnetic measurements. orders antiferromagnetically in two steps. In a first step the sublattice orders below with a collinear moment arrangement along the shortest axis a which persists down to . Below a reorientation of the moments takes place. Simultaneously the moments order with a collinear arrangement along c. The ordering of the and sites is associated with the wavevector q = (010) and is described by the monoclinic magnetic space group . At 1.4 K the ordered moment values of and are and , respectively. The moment is tilted away from the x-direction by an angle of and by from the y-direction within the (0yz) plane. The resulting structure corresponds to a three-dimensional canting with six sublattices. The presence of diffuse scattering in the 16.5 - 53 K temperature interval is attributed to short-range ordered magnetic domains of the mean correlation length A. Fourier analysis of the data reveals that the first- (up to 4.5 A) and third- (6.5 - 7.5 A) neighbour correlations are mainly ferromagnetic; the second (4.5 - 6.5 A) and fourth (7.5 - 8.5 A) ones are antiferromagnetic. The magnetic ordering of the coexisting novel phase with the structure type (space group P6/mmm) has been also studied. The Tb moments order antiferromagnetically below . This collinear moment arrangement is associated with the wavevector and is described by the magnetic space group . At and is confined to the (001) plane.

Magnetic properties of RFe6Ga6 compounds (R = Gd, Dy, Ho, Er, Tm)

We have studied the magnetic properties of several ternary rare-earth compounds of the composition RFe 6 Ga 6 (R = Gd, Dy, Ho, Er, Tm) by means of magnetization measurements in high fields up to 35 T. All these compounds cystallize in the tetragonal ThMn 12 type of structure. This structure has three non-rare-earth sites. Previous neutron-diffraction studies have shown that the Fe and Ga atoms preferentially occupy the 8f and 8i sites, respectively. These two types of atoms share the 8j site. The RFe 6 Ga 6 compounds have magnetic ordering temperatures somewhat above 500 K. At 4.2 K, the net magnetization is fairly small because of the mutually compensating effect of the R- and Fe-sublattice magnetizations. Under these circumstances, the high-field free powder method, used by us previously, offers the possibility to study the intersublattice magnetic coupling in these materials. For all five compounds investigated, we have determined experimental values of the intersublattice-coupling constants. Our results are discussed in terms of the systematics derived previously for the behaviour of the intersublattice-coupling strength in a variety of different types of R-Fe intermetallics.

Low-temperature magnetisation and specific heat in antiferromagnetic rare-earth germanides of the type R3Ge4

We have studied the magnetic properties of R3Ge4 compounds with R = Dy and Er by means of specific heat measurements. Both compounds show specific heat anomalies indicative of a two-step magnetic ordering upon cooling. The results are discussed together with neutron diffraction data.