Extracting Sample Magnetometer Research Articles

Structure and magnetic properties of RFe9Mn3 compounds with R=Y, Tb, Dy, Ho and Er

Following the discovery of Nd2Fe14B compound [1] which has been treated as the third generation of the rare earth permanent magnets, the Sm2Fe17 carbides and nitrides [2] with the rhombohedral Th2Zn17-type structure, and Nd(Fe,Ti)12 nitrides [3] with the ThMn12type structure have been found possessing excellent intrinsic permanent magnetic properties. So the iron rich rare earth-transition metal compounds (RnTm) become new potential candidates for permanent magnet applications, and the study of these compounds is attracted intensively world wide. To understand the influence of these interstitial atoms it is necessary to first understand better the interactions that are present in the parent compounds. In this letter, the magnetic properties like the Curie temperature and the saturation magnetization in RFe9Mn3 (R = Y, Tb, Dy, Ho and Er) compounds have been investigated. The mean-field constants of DyFe9Mn3 and HoFe9Mn3 compounds have also been calculated. The Mn element has been chosen because it can show some very interesting magnetic behaviors such as large magnetic moment in some compounds. All the RFe9Mn3 samples with R = Y, Tb, Dy, Ho and Er were prepared by argon arc melting from starting materials of at least 99.5% purity. The alloys were melted five times to ensure homogeneity. After arc melting, the polycrystalline specimens were sealed into evacuated quartz tubes and annealed at 1073 K for 50 h and then quenched into water. The phase composition, the structure and the lattice parameters for the RFe9Mn3 compounds with R = Y, Tb, Dy, Ho and Er were determined by means of the X-ray diffraction (XRD) patterns of free powder samples. Fig. 1 shows the X-ray diffraction patterns of RFe9Mn3compounds with R = Y, Tb, Dy, Ho and Er. The lattice constants a, c and the unit-cell volume V are shown in Table I. It can be seen that all of the investigated compounds are single phase and crystallized in ThMn12-type structure. The lattice constants a, c and the unit cell volume V decrease with increasing atomic number from Tb to Er, reflecting the lanthanide contraction. The specific magnetization was measured on free powder with an extracting-sample magnetometer at 5 K

Effects of Co addition on magnetic properties and nanocrystallization in amorphous Fe84Zr3.5Nb3.5B8Cu1 alloy

The structure, Curie temperature, and magnetization of (Fe1−xCox)84Zr3.5Nb3.5B8Cu1 (x=0.0–0.8) alloys were investigated by x-ray diffractometer, differential scanning calorimeter, magnetic balance, and extracting sample magnetometer, respectively. The bcc grains are embedded in the amorphous matrix after controlled annealing. The crystallization temperature Tx of the amorphous alloy decreases with the increasing Co content, whereas the Curie temperature Tc of the amorphous alloy is enhanced by an increase in Co content. The magnetization measured under the field of 60 kOe at a temperature of 1.5 K is enhanced first by the increase of Co addition, and exhibits a maximum at the composition where x=0.2, then decreases while Co content increases.

Studies on the Magnetic Anisotropy and the Coercivity of Granular γ-Fe2O3 Powders

The granular γ-Fe2O3 powders are prepared. The particle shapes and mean particle sizes of the samples are determined by Transmission Electron Microscopy (TEM). Using Extracting Sample Magnetometer (ESM) and Vibrating Sample Magnetometer (VSM), the magnetic parameters are measured at different temperatures. By the Law of Approach to Saturation (LATS), the effective magnetic anisotropy constants KE of granular γ-Fe2O3 powders at different temperatures are obtained. By using the mixed-coercivity model, a good explanation is given to the temperature dependence of the coercivity for granular γ-Fe2O3. It is found experimentally, for the first time, that the variation tendency of KE with temperature for granular γ-Fe2O3 is about the same as that of the shape magnetic anisotropy Ksh, and that the magnetization reversal process of granular γ-Fe2O3 is close to uniform rotation at different temperatures.

The interface magnetization of ultrafine Ni particles coated by NiO and Ni/NiO multilayers

Ultrafine Ni particles (Ni-UFPs) have been prepared by the gas condensation method. The surfaces of these particles were oxidized to form a layer of NiO. Ni/NiO multilayers (Ni/NiO-MLs), with a period of about 100 Å, were produced by the Ar + beam sputtering method. The magnetic properties of the MLs and UFPs were measured by means of an extracting sample magnetometer. For both UFPs and MLs, the experimental M- T curves (1.5 K < T < 300 K under H = 40 kOe) obey Bloch's law ( T 3 2 relation), except for an extra enhancement at low temperatures. An irreversible magnetization from ZFC to FC was found in NiO-coated Ni-UFPs, which is attributed to surface (or interface) spin-pinning. The magnetization approach to saturation was measured at 1.5 K. The experimental M- H data were fitted to the empirical law of approach to magnetic saturation by the least-squares method. The results suggest that there is a great number of disorder-like spin structures at the interfaces of both NiO-coated Ni-UFPs and Ni/NiO-MLs.

Diacetylenes containing alpha nitronyl nitroxide---- crystal structure and magnetic study

The crystal structure of mono-∝-nitronyl nitroxide substituted diacetylene was reported. The static magnetic properties of both mono-∝-nitronyl nitroxide substituted diacetylene 1 and bis-∝-nitronyl nitroxide substituted diacetylene 2 were measured with EXTRACTING SAMPLE MAGNETOMETER, and the results indicated that compound 1 possessed antiferromagnetic properties while compound 2 showed ferromagnetic properties. Furthermore, we discussed briefly the relationship between the crystal structures of these two compounds and their magnetic properties.

Synthesis, characterization and magnetic studies of 2-(4′-(p-nitrohenyl-1′, 3′ -butadienyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy-3 -oxide

The title compound was synthesized and its structure was established by IR, ESR, FAB-MS, EA and x-ray diffraction. Using the Extracting Sample Magnetometer, we studied the static magnetic properties of this compound, and the results indicate that ferromagnetic interaction exists in the title compound. In addition, the analysis for the transition metals was conducted, and it can be concluded that the observed ferromagnetic properties are not due to the contamination of transition metals. Structure-property correlation will also be discussed.

Temperature dependence of the magnetic properties of the rare-earth-transition-metal intermetallic Lu 2Fe 14C

Magnetization curves of the ternary tetragonal compound Lu 2Fe 14C were measured in an extracting-sample magnetometer in the temperature range from 1.5 to 300 K. The temperature dependence of the magnetic properties of Lu 2Fe 14C is discussed.

Curie temperature, magnetic moment, and high-field susceptibility of amorphous Fe90-XSiXZr10 alloys

The magnetization curves at 1.5K and thermomagnetization curves in the fields of about 450e for amorphous Fe90-XSiXZr10 (x = 0, 4, 7 and 10) alloys prepared by the drum spinning technique are measured with an extracting sample magnetometer. At low Si concentration the amorphous Fe90-XSiXZr10 alloys exhibit a large value of the high-field susceptibility, but the average magnetic moment per Fe atom μFe, and the Curie temperature, Tc, are quite small, compared with amorphous Fe87-XSiXB13 alloys. This unusual behavior could be explained in terms of the presence of the antiferromagnetic states.

The scattering mechanism of resistivity in amorphous Fe 90− xCo xZr 10 alloys

The reduced resistivities of amorphous Fe 90− x Co x Cr 10 alloys have been studied in the temperature ranges 4.2–300 K and 300–900 K by the fourprobe method. The magnetization was measured with an extracting-sample magnetometer and the Curie temperatures were measured with a magnetic balance. In the low cobalt concentration range 0 ⩽ x ⩽ 20, the resistivity curves exhibit a minimum around the Curie temperature T C, which can be explained by the coherent exchange scattering model. In the high cobalt concentration range 20 ⩽ x ⩽ 90, a Kondo-like resistivity minimum is observed at very low temperatures. At higher temperatures ( T ⩽ T cr − 100) there exists a change from Ziman behaviour ϱ ∞ T to ϱ ∞ T 1 2 for 0 ⩽ x ⩽ 90, which can be considered to be the result of scattering by phonons, when the wavelength of the phonon is greater than the electron mean free path.

THE MAGNETIC PROPERTY OF AMORPHOUS Pr-Co THIN FILMS

Amorphous thin films of PrxCo1-x alloys were prepared over the composition range 0.06-0.86 by the vacuum evaporation method with two sources. The magnetic properties of those films were measured by using extracting sample magnetometer, vibrating sample magnetometer and the alternating susceptibility set. The dependence of magnetization of these films on temperature and field were studied. It was found that the magnetization has a sudden drop near the temperature corresponding to the maximun of the value of the alternating magnetic susceptibility, and for samples with xco and Pr atom μpr were calculated. The effective magnetic moment of Co atom μco equals l.36f(x), where f(x) is the probability for bearing magnetic moment of cobalt atoms. The effective magnetic moment of Pr atom equals 1.6 μB in. the composition range 0-40% and decreases rapidly in the range 0.4-0.86.