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Pb(Mg1/3Nb2/3)O3-PbTiO3nanoparticles were synthesized by solid-state route. The crystal structure and optical properties were characterized by X-ray diffraction and UV–visible spectroscopy. X-ray diffraction confirmed the perovskite structure and the mean size of the crystallites was determined by employing the Williamson–Hall (W–H) model. From the UV–Visible measurements, several fundamental optical properties such as transmittance, absorbance, refractive index, band gap (Eg), Urbach energy, optical conductivity, dielectric function, and absorption coefficient were determined. The band gap energy was found to be around 3.05 eV with a high transmittance value for high wavelength. Further, the optical data were utilized to investigate the linear susceptibility, third-order nonlinear optical susceptibility, and nonlinear refractive index of the sample. It is found that the values of χ(1), χ(3) and n2were equal to 0.053 esu, 1.33 × 10−15esu, and 3.88 × 10−14esu, respectively.

Amorphous FexNi80−xB12Si8alloys (x=0.10to 16) were fabricated by employing wheel melt spinning process. Measurements of magnetization were made over temperature range of 4.20–360K and with an applied magnetic field up to 160kOe. By making a substitution Ni by Fe, the TC(Curie temperature) was actually discovered to rise. The spin wave (SW) theory was used to examine the magnetism at low temperatures. At low temperatures (4.20K), magnetization curves were found to obey Bloch’s T3∕2law. Certain important parameters were determined, such as the constant D(SW stiffness) and the distance between interatomic transition metals (rTM−TM)for the different compositions. We employed the law of approach to magnetic saturation to obtain some important parameters, including a random magnetic anisotropy constant (KL)and then the anisotropy local correlation length. So, it’s worth noting that as Fe concentration rises, the exchange constants, random magnetic anisotropy constant (KL), and also the ferromagnetic correlation (Rf)rise.

Crystal structure, magnetic properties and magnetocaloric effects (MCE) of La1–xBixFe11.4Si1.6(x=0.0 and 0.1) compounds were investigated by X-ray diffraction and magnetization measurements. The La1–xBixFe11.4Si1.6compounds presented a cubic NaZn13type structure. First, the magnetization behavior and the magnetic transition were analyzed in terms of Landau theory. Then, Bi substitution for La in La1–xBixFe11.4Si1.6compounds led to a decrease in magnetic entropy change () but an increase in Curie temperature (TC) significantly. The significant increase of TCby Bi substitution from 202.5 to 256 K for x=0.0 and x=0.1 respectively was attributed to an increase in the Fe-Fe exchange interactions. Moreover, magnetocaloric effect was calculated in terms of isothermal magnetic entropy change. The maximum values of () of La1–xBixFe11.4Si1.6for x=0.0 and 0.1 compounds were found to be, respectively, 22.56 and 4.36 J/(kg·K) under an applied magnetic field change of 5 T. For the same applied magnetic field (μ0H=5 T), the relative cooling power (RCP) values were found to vary between 487 and 296 J/kg.

Abstract The magnetization of Fe/Pt multilayers has been measured as a function of temperature. For Fe/Pt multilayers with fixed iron layer thickness of 2.5 Å, the magnetization decreases faster with temperature as the platinum layers are made thicker. A simple theoretical model has been used to explain the temperature dependence of the magnetization. From the model the approximate values for the bulk exchange interaction Jb and the interlayer coupling strength JI for various Fe/Pt multilayers have been obtained.

The magnetization of Co(tCo)/Pt(tPt) (4 Å≤tCo≤10 Å, 7 Å≤tPt≤20 Å) multilayers has been measured as a function of temperature. For Co/Pt multilayers with fixed cobalt layer thickness of 4 Å, the magnetization decreases faster with temperature as the platinum layers are made thicker. A simple theoretical model based on an anisotropic ferromagnetic system has been used to explain the temperature dependence of the magnetization and the approximate values for the in-plane exchange interaction J0and the interlayer coupling strength J1for various Co/Pt multilayers have been obtained.

Amorphous Fe100−XErXfilms, with 8

Temperature and compositional dependences of magnetization of Fe100−XErXsputtered films (with 8

Amorphous (Fe1—xGdx)80B20 alloys have been prepared by melt spinning technique and their magnetic properties have been studied. The Gd moment at 10 K is found to be 7μB which agrees with the theoretical value indicating a collinear spin structure. The magnetic compensation at 10 K occurs for x close to 0.195. The mean-field theory has been used to explain the temperature dependence of the magnetization. The exchange interactions between Fe–Fe, Fe–Gd and Gd–Gd atom pairs have also been evaluated. From an analysis of the approach to saturation magnetization, the local random anisotropy constant KL has been extracted. It is found that KL decreases with increasing Gd concentration. This result suggests that the substitution of Fe with Gd seems to favor the increase of magnetic order by reducing the random anisotropy.

We have studied the magnetization of melt-spun amorphous Fe80—y—xNiyMnxB12Si8 alloys with 20 ≤ y(Ni) ≤ 50 and 0 ≤ x(Mn) ≤ 2 under magnetic fields up to 18 kOe, and have analyzed the results at 4.2 K, based on the random magnetic anisotropy (RMA) model. The approach to saturation is established in the form of H—1/2 for the various samples. The exchange constant A and the ferromagnetic correlation length Rf decrease with Mn addition while the local random anisotropy is enhanced.

The influence of the addition of a few atomic percent of Er on the magnetic properties of amorphous Co-B alloys has been investigated. With increasing Er content (decreasing B content), the magnetic moment of the Co atom increases up to x= 4. The temperature dependence of the magnetization of the samples has been studied. Spin echo nuclear magnetic resonance measurements were carried out at 4.2 K.

We have studied the magnetization of melt spun amorphous Fe80−xVxB12Si8alloys with 0 ≤ x≤ 15 under high magnetic fields up to 150 kOe, and have analysed the results at different temperatures based on the random magnetic anisotropy model. We have extracted the length over which the local anisotropy axes show a correlation. The exchange constant Adecreases from 37 × 10−8to 11 × 10−8erg/cm as the V concentration increases from 0 to 15. The local random anisotropy constant KLis found to decrease with increasing temperature. Experimental data show that the ferromagnetic correlation length Rfincreases with increasing temperature.

Abstract: Amorphous Fe80ErxB20-x ribbons (0

Several series of CoNi/Au multilayers were investigated using different X-ray diffraction methods. The compositions and thicknesses of the Co Ni layers were varied, and the influence of temperature treatment of gold buffer on the quality of the multilayers was studied. According to the results, the quality of the multilayers is influenced primarily by the roughness of the substrate and the buffer. The CoNi/Au multilayer systems grow predominantly with a replicative, highly correlated roughness induced by the substrate and buffer roughness. A cumulative roughness was found only rarely. In contrast, a decrease in the original roughness towards the sample surface was found for certain deposition parameters. Keywords: Cobalt; Multilayers; Nickel; X-ray diffraction

Amorphous Co79 - x - yErxB21 + yalloys, with x< 10 at.% and y< 3 at.%, belong to the series of ternary transition metal-rare earth-metalloid glasses of great interest for their high coercivity and magnetization. An anomalous wide angle X-ray scattering study has been performed on a series of metallic glasses in order to relate their magnetic behaviour to their local and medium range order. Due to the large difference in size and electronic number, Z, between the three components, this technique allows the determination of the surroundings of the cobalt and erbium atoms and the discrimination of the CoCo, ErEr and CoEr correlations in the first coordination shell. A competition between the topological disorder and a chemical ordering in the short and medium range occurs when the Er content increases, which may influence their magnetic and thermodynamic properties.

We have prepared Co86Tb14/Pt multilayers by r.f. sputtering and studied their magnetic and magneto-optical properties. As the Co–Tb layer thickness (tCoTb) decreases below 200Å the saturation magnetization increases, the rectangularity of the M–Hloops and the coercivity decrease. The effective anisotropy Keffof the multilayers was determined by a torque magnetometer. The product Keff×tCoTbshows a linear dependence with tCoTbas normally found for the superlattices yielding the bulk and surface anisotropies of 1×106ergcm−3and −0.2ergcm−2, respectively. These results are explained in terms of an interfacial Co–Pt layer. The polar Kerr rotation for the multilayers is found independent of layer thickness and is equal to 11.5min, which is higher than the single thick layer.

We investigated the magnetocaloric effect in commercial Er2O3powders which presents almost no hysteresis losses at low temperature. At a magnetic field change of 5 T, it displays large magnetic entropy change (−ΔSM)maxof 15.02 J/(kg.K) and a refrigerant capacity (RC) of 311 J/K at Néel temperature TN = 3.32 K. The magnetic transition was found to be of a second-order. The maximum values of adiabatic temperature change (ΔTad)maxreach 0.70 K for a magnetic field change of 1 T. The large value, of (−ΔSM)maxas well as no hysteresis loss, makes Er2O3a promising material as a magnetic refrigerant at low temperature.

The magnetic properties of amorphous Co100−xZrxfilms prepared by co-evaporation have been studied by means of vibrating sample magnetometry and ferromagnetic resonance. The temperature dependence of spontaneous magnetization Msin the low temperature range can be described using Bloch’s law. In addition, the spin wave stiffness constant, the distance between nearest magnetic atoms and the exchange interaction between cobalt and its nearest neighbors were calculated from the experimental results for x=27. Spin-wave resonance modes were obtained and the change of the resonant field as a function of the mode number nobeys the so-called n2law perpendicular to the film plane at 300K.

We report on the effect of Carbon insertion on the microstructure and magnetic properties of nanocrystalline Pr2Co7Cx(x≤1). The Pr2Co7Cxwere characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and physical property measurement system (PPMS9) Quantum Design. Mean field theory was utilized to depict the temperature dependence of magnetization and deduce the exchange interactions. The approach to saturation magnetization was as well used. The results were interpreted in the framework of random magnetic anisotropy model. From such analysis, some fundamental parameters were extracted.

Co/Mn multilayers were prepared using evaporation technique under ultra-high vacuum conditions and their structural and magnetic properties were studied. The temperature dependence of the spontaneous magnetization Ms(T)was recorded for different cobalt layer thickness (tCo) ranging from 19Å to 70Å. Bloch’s law describes satisfactory the thermal change of magnetization for all samples. In addition, the change of the spin-wave (SW) parameter B3∕2versus tCowas discussed. The torque magnetometry was utilized to extract the effective anisotropy (Keff) and the interlayer coupling constant (JI) was determined from the in-plan M–H loops. An updated model based on SW theory was applied to describe the M(T)variation and to calculate the approximate values of exchange interactions for samples with different Co-layer thicknesses.

Fe/Pt multilayers with constant ePt= 1.5 nm and varied eFein the range 0.2–5.4 nm are studied by Mössbauer spectrometry and X-ray diffraction. For eFe< 2.0 nm, the 57Fe Mössbauer spectrum is typical of a disordered magnetic interface phase. For higher thicknesses, in addition to this phase, a bcc iron phase is also observed, giving evidence that the thickness of the iron layer is thick enough to allow its centre to be constituted of pure iron. For magnetic spectra, the magnetic anisotropy was always found in the plane of layers.