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The Pt/Co/Pt trilayer system is widely studied for its perpendicular magnetic anisotropy (PMA). In this work we delve into the effects of thermal annealing from the perspective of magnetic domain wall dynamics. We find that the coercivity of the films remains constant while the domain wall velocity decreases drastically with thermal annealing (≤ 473 K). The decrease in the creep scaling constant with annealing temperature, confirm the enhanced pinning effect. Our results demonstrate that annealing temperature can significantly affect the magnetic micro-structure as well as magnetic domain dynamics in Pt/Co/Pt films with PMA. • Pt/Co/Pt with perpendicular magnetic anisotropy is studied. • Domain wall velocity measurements in Pt/Co/Pt with in-situ annealing are reported. • Decrease in the creep scaling constant with annealing temperature is observed. [ABSTRACT FROM AUTHOR]

We report on the magnetic and Mössbauer properties of polycrystalline HoFe 1- x Cr x O 3 (0≤ x ≤1) compounds. Magnetization data reveals the continuous tailoring of magnetic transition due to weakening of Ho 3+ -Fe 3+ and Fe 3+ -Fe 3+ interactions in the entire temperature range by replacing the Fe 3+ ions with Cr 3+ ions. The observed decrease in Néel temperature (T N ) and increase in spin re-orientation transition temperature (T SR ) with the replacement of Fe 3+ with Cr 3+ is ascribed to the weakening of Fe(Cr)-O-Fe(Cr) antiferromagnetic exchange interaction. In addition, we also attribute such a change in T N to the enhancement of ferromagnetic interaction of adjacent Cr 3+ moments through t - e hybridization as a result of the structural distortion. The decrease in isomer shift (IS) suggests enhancement of the interaction between nuclear charge with the 3 s electrons as a result of decrease in radial part of 3 d wave function with Cr addition. In this paper we also discuss about the variation of quadrupole splitting (QS) and hyperfine fields (H hf ) with Cr addition in HoFe 1- x Cr x O 3 (0≤ x ≤1) compounds. [ABSTRACT FROM AUTHOR]

Using different experimental techniques such as X-ray reflectivity, X-ray diffraction, X-ray photoelectron spectroscopy and magneto-optical Kerr effect (MOKE) microscopy, the structural and magnetic properties of Ni films grown on Si substrates are investigated. Various Ni-silicide phases are found to be formed at the Ni–Si interface as a function of depth following the sequence Ni-Ni 2 Si-NiSi-NiSi 2 from the nickel to silicon side. This has been explained in terms of the effective heat of formation and inter-diffusion of the elements at the interface. In-plane magnetic anisotropy of the system is investigated by measuring in-plane magnetization using MOKE microscopy. The film exhibits an uniaxial in-plane magnetic anisotropy. An anomalous behavior, i.e., the collapse of the hard axis, has also been observed. This anomaly has been explained in terms of the creation of V-state domains during the magnetization reversal process at the hard axis. Interestingly, in-plane magnetic anisotropy could not be found in a Ni film grown with a Pt buffer layer on the Si substrate. Ni-silicide phases could not be detected in this system. This may suggests that the formation of silicides and diffusion at the interface causes the atypical magnetic anisotropy in Ni–Si sample. • Impact of interfacial nickel silicide formation on the In-plane magnetic anisotropy of Ni thin film. • The collapse of hard axis is explained by the formation of V-state domains. • Formation of different Ni silicide like Ni 2 Si, NiSi and NiSi 2 forms at the Ni/Si interface. [ABSTRACT FROM AUTHOR]

Polycrystalline magneto-electric ( ) ceramics are studied with bulk magnetization and 57Fe Mössbauer measurements. The ferrimagnetic to paramagnetic transition temperature (T C ), saturation magnetization (M S ) and the magnetic anisotropy values are found to vary significantly with the site-disorder of Fe3+ and Ga3+ cations. With the increase of iron content, increase of T C and M S , and decrease of magnetic anisotropy are observed. Using low temperature high magnetic field 57Fe Mössbauer measurements, individual temperature dependence of hyperfine fields and hence magnetization of the three sub-lattices are measured. It is observed that the three sub-lattices have quite a different temperature dependence resulting in the non-monotonous variation of resultant magnetization as measured by bulk magnetic measurements. Definite evidence, using 57Fe Mössbauer measurements, is submitted to show that the Fe ions at Fe2 and Ga2 sites are responsible for the observed magnetic anisotropy, site-disorder induced magnetism and thermo-magnetic irreversible features in . [ABSTRACT FROM AUTHOR]

Abstract: The present work reports the preparation and room temperature Raman study of polycrystalline magnetoelectric BiFeO3 (BFO) material. All the 13 Raman modes predicted by group theory (Γ Raman,R3c=4A 1+9E) for R3c structure of BFO are observed in the present work. To distinguish A 1 and E modes, Raman measurements have been carried out in parallel and crossed polarization configurations. In addition to other modes, intense sharp peaks corresponding to A 1-1, A 1-2, and A 1-3 modes at 135.15±1.38, 167.08±0.34 and 218.11±0.45cm−1, respectively, are clearly observed in the polycrystalline BFO sample. The results of Raman spectra matches well with the recently reported single crystal and epitaxially grown thin film of BFO. Further, X-ray diffraction (XRD), differential scanning calorimetry (DSC), Mossbauer spectroscopy, vibrating sample magnetometer are used to characterize the sample. The XRD result shows BFO as a major phase along with about 1% impurity phase. Mossbauer spectrum show sextet at room temperature indicating the magnetic ordering. The observed isomer shift indicates the presence of Fe in trivalent oxidation state. DSC is used to find the Neel temperature (T N). The observed hyperfine parameters and T N match well with the literature. The room temperature magnetization measurement indicates the anti-ferromagnetic nature of the BFO sample. [Copyright &y& Elsevier]

• Cationic ordering and the element-specific magnetic moments. • Ferromagnetic coupling of Gd3+ and Dy3+ substituted ions to the Fe3+/Ni2+ at B-site. • Collinear ferrimagnetic structure with the partially inverted spinel structure. Cationic distribution and magnetic properties of partially rare-earth (R) doped NiFe 2 O 4 (NFO) compounds, i.e. NiFe 2- x R x O 4 (x = 0 and 0.075; R = Gd, Dy and Ho) were investigated, and the results are discussed and presented in this paper. All the compounds were found to stabilize in the cubic inverse spinel structure with the space group Fd 3 - m. The analysis of the results based on X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements are primarily focused on the valence state information of constituting rare-earth or transition-metal ions, cationic distribution, and the coupling between their magnetic moments. The XAS data revealed that nickel is in Ni2+ valence state while iron is mainly in the Fe3+ valence state though some perceptible traces of Fe2+ were observed. The rare-earth ions are in trivalent states. The partial doping causes differences in the cationic distribution of Ni2+ and Fe3+ ions which obviously results in differences in the net Fe or Ni magnetic moments. Furthermore, 57Fe Mössbauer spectra revealed altered hyperfine field parameters upon the Gd3+, Dy3+ and Ho3+ substitution and all the compounds were found to exhibit collinear ferrimagnetic structures. The results are relevant for the investigation of orientation of individual magnetic moments and to obtain site-specific information related to all the cations involved in the rare-earth doped nickel ferrite structures. [ABSTRACT FROM AUTHOR]

Highlights • The effects of ferro-elastic domains of LaAlO 3 substrate on the magnetization reversal and magnetic anisotropy of cobalt thin film are studied. • Domain wall pinning along the twin boundary is observed. • Blocked state and single domain state are observed in the alternate region of twins. Abstract Present work reports the effects of ferroelastic domains (FE) on the magnetic properties of top magnetic layer. Cobalt film of 15 nm is deposited using electron beam evaporation technique on single crystalline LaAlO 3 (0 0 1) (LAO) substrate which consists FE structural twin domains. LAO substrate is in-situ heated above its FE transition temperature and cooled to room temperature before depositing cobalt film of 15 nm. Textured growth of cobalt film is observed in-situ from reflection high energy electron diffraction (RHEED) patterns. The presence of FE structural twins in LAO substrate is confirmed from the X-ray reciprocal space mapping measurements. From the optical polarization microscopy, it is observed that the different regions consist different modulations viz., lamellar like and square-like structures in LAO substrate. The magnetic anisotropy and magnetization reversal is studied ex-situ using magneto-optical Kerr effect (MOKE) microscopy with different spatial resolutions. The analysis of azimuthal variation of coercivity ( H C ) shows the superposition of two-, four- and six- fold anisotropy contribution at different regions of the sample. Twofold anisotropy and weak sixfold anisotropy may due to magneto-crystalline anisotropy, whereas the fourfold anisotropy might be coming because of square-like modulations of the substrate. Moreover, MOKE microscopy reveals the domain wall pinning along the twin boundaries (FE) due to which magnetization reversal is proceed by three distinct mechanisms when field is applied away from easy axis of magnetization and lamellar pattern. As a consequence of this, magnetization reversal proceeds by 'labyrinth switching' and abrupt magnetic domain wall switching within individual FE domains. [ABSTRACT FROM AUTHOR]

Highlights • Poly-crystalline gadolinium iron garnet thin film is studied with MOKE microscopy measurements. • Oblique magnetic anisotropy is observed at room temperature. • The observation of magnetic compensation is manifested by the inversion of MOKE loops. • The magnetic domain size increase in the vicinity of compensation point and Curie temperature. Abstract The present work reports the preparation and magneto-optical Kerr effect (MOKE) microscopy study of gadolinium iron garnet Gd 3 Fe 5 O 12 (GdIG) polycrystalline thin film. The GdIG thin film is grown on Si(0 0 1) by Pulsed laser deposition technique (PLD). Grazing angle X-ray diffraction confirms the formation of GdIG after ex-situ annealing at 750 ° C under ambient conditions. MOKE measurement done in both longitudinal and polar geometries shows oblique magnetic anisotropy axis at room temperature rather than either completely in-plane or out of plane anisotropy axis. Signatures of magnetic compensation are seen from the increase of coercive field obtained from temperature dependent MOKE measurements. The observation of magnetic compensation is also manifested by the inversion of MOKE loops. The magnetic domain structure shows the formation of bubble or maze-like domains with a considerable dependence on temperature. The observed domain size variation as a function of temperature is fitted considering the model for thermally activated behavior of domain size variation in rare-earth garnets. [ABSTRACT FROM AUTHOR]

Magnetization reversal and magnetic microstructure of top soft magnetic layer (Fe) in exchange spring coupled L1 0 FePt/Fe is studied using high resolution Kerr microscopy. With remnant state of the hard magnetic layer (L1 0 FePt) as initial condition, magnetization loops along with magnetic domains are recorded for the top soft magnetic layer (Fe) using Kerr microscopy. Considerable shifting of Fe layer hysteresis loop from center which is similar to exchange bias phenomena is observed. It is also observed that one can tune the magnitude of hysteresis shift by reaching the remanent state from different saturating fields ( H SAT ) and also by varying the angle between measuring field and H SAT . The hysteresis loops and magnetic domains of top soft Fe layer demonstrate unambiguously that soft magnetic layer at remanent state in such exchange coupled system is having unidirectional anisotropy. An analogy is drawn and the observations are explained in terms of established model of exchange bias phenomena framed for field-cooled ferromagnetic - antiferromagnetic bilayer systems. [ABSTRACT FROM AUTHOR]

• The temperature dependent Raman studies of SrFe8Co2Ti2O19 M- type hexaferrite are reported. • Spin phonon coupling is observed in SrFe8Co2Ti2O19 Y- type hexaferrite. • The In-field Mossbauer spectroscpic studies confirm the Fe3 + ions distribution at different crystallographic sites. Structural, magnetic, in-field 57Fe Mössbauer and Raman studies of SrFe 8 Co 2 Ti 2 O 19 polycrystalline magneto-electric hexaferrite are reported in this article. From bulk magnetization measurements, a transition is observed at 330 K, which is ascribed to a conical like magnetic transition. The population of spin-up and spin-down sites at tetrahedral and octahedral sites are calculated from in-field 57Fe Mössbauer spectroscopic studies. Furthermore, the observed cation distribution suggests that the Co2+ ions occupy the spin-down 4f 2 octahedral site, which is reported to stabilize the conical magnetic structure and is expected to play an important role in the magneto-electric properties. Temperature-dependent Raman spectroscopy studies confirmed the spin-phonon coupling in the prepared sample. [ABSTRACT FROM AUTHOR]

We report the structural and magnetic properties of four-layer Aurivillius compound Bi 5 FeTi 3 O 15 (BFTO) at high hydrostatic pressure conditions. The high-pressure x-ray diffraction (XRD) data does not explicitly show structural phase transitions with pressure, however the observed changes in lattice parameters indicate structural modifications at different pressure values. In the initial pressure region values (up to 2.2 GPa), the lattice parameters a - and b - are nearly equal implying a quasi-tetragonal structure, however as the pressure increases a - and b - diverges apart and exhibits complete orthorhombic phase at pressure values of about ≥ 8 GPa. Principal component analysis (PCA) of high pressure Raman measurements point out an evident change in the local structure at about 5.5 GPa indicating that the evolution of the local structure under applied pressure seems to not follow crystallographic changes (long range order). Nuclear forward scattering (NFS) measurements reveal the development of magnetic ordering in BFTO at 5K with high pressures. A progressive increase in magnetic order is observed with increase in pressure at 5 K. Further, NFS measurements carried out at constant pressure (6.4 GPa) and different temperatures indicate that the developed magnetism disappears at higher temperatures (20 K). It is attempted to explain these observations in terms of the observed structural parameter variation with pressure. • Four-layered Aurivillius Bi 5 FeTi 3 O 15 is studied with hydrostatic pressure. • Structural modifications are observed in the studied pressure range. • Development of magnetism is observed with pressure at 5 K. [ABSTRACT FROM AUTHOR]

Structural, Raman spectroscopy, leakage current density, temperature dependent magnetization and Mössbauer measurements of polycrystalline DyFeO 3 (DFO) prepared through sol–gel route are reported in this paper. Phase purity and structure of the prepared sample is confirmed from x-ray diffraction and Raman spectroscopy measurements. The room temperature leakage current density ( J – E ) measurements indicate that Ohmic contribution and space charge limited conduction are the dominating mechanisms at low and high applied electric fields respectively. Signatures of Fe 3+ spin reorientation transition ( T SR ) and the antiferromagnetic ordering of Dy 3+ ions are observed from the temperature dependent (10–350 K) magnetization data. The M – H data measured at 2 K shows the field induced metamagnetic transition. Internal hyperfine field obtained from temperature dependent (5–300 K) 57 Fe Mössbauer measurements is observed to decrease below the T SR and further found to increase till 5 K indicating the contribution of Dy 3+ magnetic ordering on the hyperfine field of Fe nucleus. [ABSTRACT FROM AUTHOR]

The structural, magnetic, and in-field 57 Fe Mössbauer studies of Ba 0.5 Sr 1.5 Zn 2 Fe 12 O 22 polycrystalline multiferroic, which belongs to Y-type hexaferrite class, are presented in this paper. Sr 2+ substitution at Ba 2+ site effects the redistribution of Zn 2+ and Fe 3+ ions at tetrahedral sites in the crystal. The magnetization data reveals the magnetic field induced transitions in the M – H curve. The in-field Mössbauer study reveals that the occupancy of Fe 3+ ions in the tetrahedral sites is more than that in the octahedral sites because of doping of Sr 2+ at Ba 2+ site, which plays an important role in field induced multiferroic property at low temperature. [ABSTRACT FROM AUTHOR]

The nanosize effects on magnetic field induced transitions in La0.67-xEuxCa0.33MnO3 (x=0.25 and 0.27) system are presented in this paper. The reduction in the particle size of the system shows drastic effects on the electrical transport properties leading to robustness of the charge ordering phenomenon. The metal-insulator transition found in bulk materials at low magnetic fields disappeared in nanoparticles of the same material and a high field induced metal-insulator transition emerged at lower temperatures. These results manifest a strong correlation between the chemical pressures induced by doping of various ions at A-site and nanosize related phenomenon. [ABSTRACT FROM AUTHOR]

• Real time growth of Fe on Ag is monitored through RHEED. • Ion beam erosion induces morphology induced uniaxial magnetic anisotropy. • Coupled Cubic and uniaxial magnetic anisotropy leads to multi jump hysteresis loop. • Magnetic domain dynamics reveals magnetization reversal through 180° and 90° domain wall motion. Growth and magnetic characterization of Fe film on ion-sculpted Ag(0 0 1) substrate have been studied in-situ using reflection high energy electron diffraction and magneto-optical Kerr effect. Fe film is found to grow epitaxially on the Ag surface and exhibits epitaxial island formation up to ∼ 1 nm film thickness. Ion beam sculpting of the substrate surface, prior to the deposition of the Fe film, induces an uniaxial magnetic anisotropy in Fe film, which couples with the cubic four-fold anisotropy of bcc-Fe, lead to the multiple-step jump in magnetic hysteresis loops. Magnetic switching and its correlation with the domain dynamics of the film, as studied by the Kerr microscopy technique, revealed a striking difference in domain structure depending upon the direction of the applied magnetic field with respect to crystallographic direction. It is found that the magnetization reversal takes place via a "single-step jump" mechanism through sweeping of 180° domain walls, whereas the combination of coherent rotation and the sweeping of 90° domain walls is responsible for a "double step jump" magnetization reversal. [ABSTRACT FROM AUTHOR]

Abstract: We have studied the valence behavior of rare-earth ions, in particular Eu-ions, in a cubic intermetallic compound which is a homogeneous solid solution of two mixed-valent compounds CePd3 and . Results of 151Eu Mössbauer spectroscopic measurements show that two different valence states, i.e., divalent- and trivalent-like states of Eu-ions exist in the compound. The possible reason for the observed heterogeneous valency vis-á-vis the variation in the chemical environment and the number of nearest-neighbor B atoms surrounding the Eu-ions has been discussed. Our results demonstrate that B incorporation in such Eu-based cubic intermetallic compounds leads to a situation where heterogeneous-valence state of Eu-ions is an energetically favorable ground state. [Copyright &y& Elsevier]

Abstract: The magnetic properties of nickel ferrite nanoparticles in the form of powders, prepared by the sol–gel process and subjected to different annealing temperatures, were investigated using both static and dynamic measurements namely hysteresis, zero field cooled–field cooled magnetization (ZFC–FC) measurements and Mössbauer spectroscopy. The Transmission Electron Microscopy (TEM) studies reveal particle sizes for the as-prepared particles which increases upto 52nm with annealing. A bimodal distribution, upto an annealing temperature of was observed. ZFC–FC measurements for the as-prepared samples reveal twin peaks, indicative of the bimodal size distribution. ZFC–FC measurements performed for fields varying from 100Oe to 3kOe show a superparamagnetic phase with blocking temperatures between 320 and . Numerical simulations for the ZFC–FC studies indicate that the signature of the bimodal size distribution can be seen only at very low fields. The variation of coercivity with particle size, as determined from the hysteresis measurements, shows a transition from a single domain to a multi domain state for particle sizes larger than 35nm. Mössbauer measurements performed at room temperature for the as-prepared sample shows a six finger pattern for the samples with higher particle size and a doublet pattern for the samples with smaller particle size, which is indicative of their superparamagnetic nature. [ABSTRACT FROM AUTHOR]

Structural, magnetic and 57Fe Mössbauer investigations of indium (In) doped cobalt ferrite are reported. Polycrystalline CoFe 2−x In x O 4 , x = 0, 0.2, 0.4, 0.6, 0.8 samples are prepared by sol–gel method. In contrast to most of the literature, in the present work phase pure samples are obtained, except for x = 0.2. The presence of ferrimagnetic ordering in all the samples is confirmed from in-field 57Fe Mössbauer spectroscopy measurements. The cation distribution is obtained unambiguously from the combined analysis of Raman and in-field 57Fe Mössbauer spectroscopy measurements. The variation of magnetic moment values calculated from the obtained cation distribution are found to match qualitatively with the experimental values, supporting the analysis of in-field 57Fe Mössbauer and Raman spectroscopy measurements. [ABSTRACT FROM AUTHOR]