Masroor Ahmad Bhat, R. A. Zargar, Anchit Modi, M. Arora and N. K. Gaur
and 8 T fields. In Table 1 the calculated values for T 0 and N(E F ) are also reported. The typical value of T 0 and N(E F ) are about 3.4 × 10 8 K and 2.4 × 10 17 eV −1 cm −3 , respectively.
The DC magneticsusceptibility (M/H) measurements for YBaCo 4 O 7 were carried out by using SQUID magnetometer as shown in Fig. 6 . In this paper, we have shown the magnetization of YBaCo 4 O 7 compound measured at 1 Tesla (T) magnetic field. From 80 K to 300 K, the data do not obey a Curie-Weiss relationship. We have collected our data for
E. Talik, L. Lipińska, A. Guzik, P. Zajdel, M. Michalska, M. Szubka, M. Kądziołka-Gaweł and R.L. Paul
line is clearly visible in the spectrum. For these lines, the background individually selected in the region limited to the particular line is subtracted and after that integration of the peak area is performed [ 56 ]. The Gaussian-Lorentzian functions were used to fit the XPS core level spectra.
Magneticsusceptibility was measured using the SQUID Magnetometer MPMS-XL-7AC (Quantum Design) in the temperature range of 2 K to 400 K.
The 57 Fe Mössbauer spectrum was recorded at room temperature using a constant acceleration spectrometer with 57 Co:Cr source. The
S.M. Kaczmarek, G. Leniec, H. Fuks, T. Skibiński, A. Pelczarska, P. Godlewska, J. Hanuza and I. Szczygieł
Na3Ln(PO4)2 orthophosphates (Ln = La, Gd) doped with Er3+ and co-doped with Cr3+ ions were synthesized by Pechini method and characterized by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. Low temperature EPR spectra were detected and analyzed in terms of temperature dependence and the structure of the obtained materials. They show that erbium and chromium ions substitute Ln3+ and also Na+ ions or Na+ channels forming complex EPR spectra. Both kinds of ions reveal ferromagnetic type of interaction which shows some anomaly at the temperature between 10 K and 15 K. Magnetic susceptibility reveals a weak antiferromagnetic kind of interaction dominating in the whole temperature range, from 3.5 to 300 K.
N. Guskos, G. Zolnierkiewicz, J. Typek, R. Szymczak, A. Guskos, P. Berczynski and A. Blonska-Tabero
Two samples containing phases formed in the FeVO4-Co3V2O8 system were prepared by a conventional sintering method. The sample designated as H5 was one-phase with the howardevansite-type structure, while the sample designated as HL7 contained a mixture of H-type and lyonsite-type structures. The temperature dependence of the electron paramagnetic resonance (EPR) spectra and static magnetic susceptibility χ was investigated in the temperature range from liquid helium to room temperature. Both the EPR spectra and the dc magnetic susceptibility showed anomalous behavior indicating that the magnetic competition process may be responsible. A comparison of the obtained results with previous studies on related compounds with the same structure, i.e. M3Fe4V6O24 (M = Mg(II), Zn(II), and Cu(II)) revealed that the observed anomaly shifted to lower temperatures on replacing the non-magnetic ions by magnetic Co(II) ions. The temperature dependence of the inverse susceptibility χ
−1 indicates the existence of antiferromagnetic interactions between Fe(III) and Co(II) spins in sample H5. The obtained values of the Curie-Weiss temperatures are lower than for the Mn3Fe4V6O24 compound and comparable to compounds from M3Fe4V6O24 systems with M diamagnetic cations. The introduction of cobalt cations intensifies the magnetic frustration what is reflected in the temperature dependence of the magnetic susceptibility at low temperatures.
Hexagonal high temperature phase β-Co2P nanorods with a diameter of around 50 nm were synthesized via a mild solvothermal route. The reaction was carried out at 180 °C using cobalt chloride hexahydrate (CoCl2 · 6H2O) as Co source and yellow phosphorous as P source. The composition, structure as well as morphology were characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS) and transmission electron microscopy (TEM). The magnetic susceptibility curve indicates that the β-Co2P nanorods show canted antiferromagnetic state, different from the paramagnetic state of orthorhombic low temperature phase β-Co2P.
Single-phase Eu3S4 was obtained via CS2 gas sulfurization of Eu2O3 nanospheres at 773 K for longer than 0.5 h. The primary particle size of Eu3S4 became larger than that of Eu2O3 during the sulfurization process. Pure synthetic Eu3S4 powders were unstable and transformed to EuS at 873 K under vacuum. Eu3S4 compacts were sintered in temperature range of 773 K to 1173 K and they transformed to EuS at 1473 K during spark plasma sintering. Specific heat of sintered Eu3S4 did not show an anomalous behavior in the range of 2 K to 50 K. The magnetic susceptibility of polycrystalline Eu3S4 followed a Curie-Weiss law from 2 K to 300 K. Magnetization of polycrystalline Eu3S4 was larger than that of single crystal Eu3S4 when the magnetic field was less than 3.5 kOe.
N. Guskos, G. Zolnierkiewicz, J. Typek, R. Szymczak and A. Blonska-Tabero
The temperature dependence of dc magnetization and electron paramagnetic resonance (EPR) spectra of the β-Cu3Fe4V6O24 multicomponent vanadate were investigated. Dc magnetic measurements showed the presence of strong antiferromagnetic interactions (Curie-Weiss temperature, Θ ∼ 80 K) at high temperatures, while zero-field-cooled (ZFC) magnetization revealed a cusp-like maximum in low fields at Tf1 = 4.4 K, which coincides with the splitting of the ZFC and FC curves. Another maximum was registered at Tf2 = 3.0 K. These two temperatures (Tf1 and Tf2) could be regarded as freezing temperatures in the spin glass state of two magnetic sublattices of Fe1 and Fe2 ions. The EPR spectrum of β-Cu3Fe4V6O24 is dominated by a nearly symmetrical, very intense and broad resonance line centered at g
eff ∼ 2.0 that could be attributed to iron ions. Below 10 K, an additional EPR spectrum with g
1 = 2.018(1) and g
2 = 2.175(1) appears, as well as a very weak line at geff = 1.99(1). The former spectrum is probably is due to divalent copper ions, and the latter line due to vanadium V4+ complexes. The temperature dependence of EPR parameters (g-factor, linewidth, integrated intensity) was determined in the range of 3–300 K. Two low-temperature maxima in the temperature dependence of the integrated intensity (at 40 and 6 K) were fitted with a function suitable for pairs of exchange-coupled Fe3+ ions. A comparison of dc magnetic susceptibility and EPR integrated intensity indicates the presence of spin clusters, which play an important role in determining the low-temperature magnetic response of β-Cu3Fe4V6O24.
Niko Guskos, Grzegorz Zolnierkiewicz, Janusz Typek, Malwina Pilarska, Constantinos Aidinis and Anna Blonska-Tabero
methods [ 1 , 3 , 10 , 11 ]. The structure contains three sublattices associated with metal ions including two sublattices with iron ions. The M ion site may be occupied by magnetic or diamagnetic ions and in case of the former one a more complex magnetic system is achieved. Measurements of DC magneticsusceptibility χ as a function of temperature showed that the Curie-Weiss behavior, χ = C/(T – ), dominates at high temperatures with a negative Curie-Weiss temperature (the largest value of was found for the compound M = Mn and the smallest for M = Cu) [ 5 , 7
Janusz Typek, Kamil Wardal, Grzegorz Zolnierkiewicz, Anna Szymczyk, Nikos Guskos, Urszula Narkiewicz and Elzbieta Piesowicz
magneticsusceptibility χ (defined as χ = M/H) in zero field cooled (ZFC) and field cooled (FC) modes of the 0.7(Fe 2 O 3 )/0.3(ZnO) nanopowder ( Fig. 2a ) and the 0.7(Fe 2 O 3 )/0.3(ZnO) dispersed in polymer ( Fig. 2b ) measured in two different magnetic fields (H = 100 Oe and 1000 Oe) is presented. In ZFC mode all magnetic moments in each single domain particle point along the nanoparticle easy axis when the nanoparticles are cooled down to very low temperature and magnetic anisotropy prevents switching of magnetization from the easy axis. As a result, the average
, which decreases steadily along with the series corresponding to the fillings of the 4f-orbitals. CeN has some unusual properties compared with the other rare-earth nitrides. It shows mixed valence behavior. The pressure induced structural phase transition of CeN is an interesting topic of research. Very little theoretical or experimental work has been reported on the structural and electronic properties of CeN. Danan et al. [ 5 ] studied the temperature dependence of lattice constant and magneticsusceptibility of CeN. Bulk calculations of CeN have been performed by