Spin Reorientation Phenomena Research Articles

Study of the Structure, Multiferroic, and Magnetic Order of Er0.9La0.1Cr0.8Fe0.2O3

Herein, the multiferroic perovskite Er0.9La0.1Cr0.8Fe0.2O3 was synthesized using the sol–gel method, and its structure and multiferroic properties were investigated. The magnetic order of Er0.9La0.1Cr0.8Fe0.2O3 was analyzed through magnetic entropy change curves. Furthermore, a four‐sublattice molecular field model was constructed to study the spin reorientation phenomena and explain the differences between various spin redirections through magnetic order correction. This work will provide a new perspective for studying the properties of type II multiferroic materials.

Insight into the negative magnetization and anomalous exchange-bias in DyFe5Al7 through neutron depolarization and neutron diffraction studies

We have provided the mesoscopic and microscopic understandings of polarity reversal of the magnetization or negative magnetization (NM) below T COMP = 93 K in an exotic magnetic material containing three magnetic sublattices, viz., DyFe5Al7 crystallizing in ThMn12 structure, using neutron depolarization and neutron diffraction techniques. A full recovery of the neutron beam polarization at the T COMP in a neutron depolarization experiment reveals a total compensation of magnetization inside the magnetic domains in the sample. The temperature-dependent neutron diffraction study under zero magnetic field has provided temperature dependencies of antiparallelly coupled Dy (M Dy(2a)) and Fe (M Fe(8f) and M Fe(8j)) sublattice magnetic moments along [100] direction. The dominance of |M Dy(2a)| over total Fe moment, , below T COMP leads to the NM in the compound. The magnetization versus magnetic field curves below the T COMP indicate the presence of field-induced spin reorientation in the compound. The magnetic field required for spin reorientation (H SR) is maximum at the lowest temperature and it decreases to zero as the temperature is increased to T COMP. Interestingly, the compound shows a finite exchange-bias (H EB) below the T COMP only, as evident from the field-cooled hysteresis loops, while at T > T COMP, H EB is almost zero. The cooling-field (H COOL) dependent study of H EB shows a slope change at H COOL ∼ H SR indicating a correlation of exchange-bias with spin-reorientation in the compound. This study, apart from revealing microscopic understanding of magnetic behavior of an exotic three magnetic sublattice system, provides a correlation among exchange-bias, magnetic compensation, and spin-reorientation phenomena.

Magnetic and magnetoelastic properties of rare earth intermetallides based on TbFe2

The paper presents the results of the study of magnetic and magnetostrictive properties of rare-earth intermetallides based on TbFe2 compound: Tb1-xZrxFe2, Tb1–xSmxFe2 and (Tb1–xYx)0.8Sm0.2Fe2. These alloys have a cubic crystal structure of the Laves phase C15 throughout the substitution region. For the system of alloys Tb1–xZrxFe2 the single-phase area is limited to the replacement parameter 0 < x < 0.2 and 0.8 < x < 1.0. The compounds of the Tb1–xSmxFe2 system were studied via X-ray dilatometry. The magnetostriction of alloys within the Tb1–xZrxFe2 and (Tb1–xYx)0.8Sm0.2Fe2 systems was studied in the temperature range of 80-320 K in magnetic fields of up to 17 kOe via a strain-gauge method. It was found that each system has the phenomenon of sign inversion of magnetostriction constants: in the system Tb1–xZrxFe2 in the area of replacement parameter x = 0.8, in Tb1–xSmxFe2 - in the area x = 0.45, and in the system of alloys (Tb1–xYx)08Sm02Fe2 at x = 0.6. It was demonstrated that magnetic compensation and spin reorientation phenomena occur in these systems. The obtained results are discussed in the model of alloys with competing exchange interactions.

Neutron Diffraction Investigation of the DyFe11Ti Magnetic Structure and Its Spin Reorientations

Abstract In this article, we report on the magnetic structure of DyFe11Ti and its thermal evolution as probed by neutron powder diffraction. A thermodiffraction technique was used to follow the temperature dependence of the magnetic moments, as well as their orientation. The Dy and Fe moments were coupled to each other in an antiparallel manner to form a ferrimagnet, where the easy magnetization direction at 2 K was the [110] axis in the basal (a, b) plane. This magnetic structure underwent two successive spin reorientation phenomena with increasing temperature. A large Dy magnetic moment of 9.7 Bohr magneton (μB) was obtained at low temperatures, and the magnitude decreased rapidly to 7.5μB at 200 K. The largest Fe magnetic moment was observed on the Fe 8i position. A ThMn12-type crystal structure was preserved in the studied temperature range, despite the large changes of the magnetic structure. A sharp tilt was observed at the first-order spin reorientation, TSR1; the angle between the easy magnetization axis and the crystal c axis was reduced from 90° at 2 K to about 20° at 200 K (where c is the easy axis above 200 K); and the Dy and Fe magnetic moments maintained an antiparallel coupling.

Strain tunable spin reorientation of an individual Fe atom on 2D blue phosphorous

Herein, using first-principles calculations, we predict spin reorientation from in-plane to out-of-plane magnetization of an individual Fe magnet at the monophosphor vacancy in two-dimensional blue phosphorous (2D blue-P) by a few percent of tensile strain. We further reveal that this magnetization reversal is associated with the spin-state transition of Fe 3d5 state from low-spin (1 ) to high-spin state (5 ), which occurs at the same tensile strain imposed into 2D blue-P, from the Ligand field theory analyses in the unpaired electron counts. The underlying mechanism for both the spin-state transition and spin-reorientation phenomena is the strain induced changes in the spin–orbit coupled adatomic and states through the strong hybridization with the P-3p orbitals. These findings open interesting prospects for exploiting stain engineering of 2D materials to manipulate magnetism and magnetization orientation of single-molecule magnets adsorbed on it.

Magnetic Properties of Nd&lt;sub&gt;3&lt;/sub&gt;Fe&lt;sub&gt;27.7-&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;Ni&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt;Ti&lt;sub&gt;1.3&lt;/sub&gt; Compounds

The structure and magnetic properties of the Nd3Fe27.7-xNixTi1.3compounds prepared by arc-melting method have been investigated by means of X-ray diffraction and magnetization measurement. It was found that all the compounds crystallized in Nd3(Fe, Ti)29-type structure with monoclinic symmetry and A2/m space group in concentration range 0.2 ≤x≤ 1.2. The unit cell volume decreased slightly with increasing Ni content. The X-ray diffraction patterns of the magnetically aligned samples showed that all compounds investigated had planar anisotropy. The Spin reorientation phenomena occurred in all the compounds. As the increase of Ni content, the Curie temperature TCmonotonously increased, but the spin reorientation temperature Tsrdid not obviously change. The saturation magnetization Ms of the compounds decreased monotonously with increasing Ni content at 5 K, 105 K, 205 K, and 305 K. The anisotropy fields Baat 5 K, 305 K and anisotropy constant K2at 305K appeared as a minimum, but the anisotropy constant K1at 305 K appeared as a maximum onx= 0.6.

Observation of re-entrant spin reorientation in TbFe1-xMnxO3.

We report a spin reorientation from Γ4(Gx, Ay, Fz) to Γ1(Ax, Gy, Cz) magnetic configuration near room temperature and a re-entrant transition from Γ1(Ax, Gy, Cz) to Γ4(Gx, Ay, Fz) at low temperature in TbFe1−xMnxO3 single crystals by performing both magnetization and neutron diffraction measurements. The Γ4 − Γ1 spin reorientation temperature can be enhanced to room temperature when x is around 0.5 ~ 0.6. These new transitions are distinct from the well-known Γ4 − Γ2 transition observed in TbFeO3, and the sinusoidal antiferromagnetism to complex spiral magnetism transition observed in multiferroic TbMnO3. We further study the evolution of magnetic entropy change (−ΔSM) versus Mn concentration to reveal the mechanism of the re-entrant spin reorientation behavior and the complex magnetic phase at low temperature. The variation of −ΔSM between a and c axes indicates the significant change of magnetocrystalline anisotropy energy in the TbFe1−xMnxO3 system. Furthermore, as Jahn-Teller inactive Fe3+ ions coexist with Jahn-Teller active Mn3+ ions, various anisotropy interactions, compete with each other, giving rise to a rich magnetic phase diagram. The large magnetocaloric effect reveals that the studied material could be a potential magnetic refrigerant. These findings expand our knowledge of spin reorientation phenomena and offer the alternative realization of spin-switching devices at room temperature in the rare-earth orthoferrites.

Hedgehog spin texture and competing orders associated with strains on the surface of a topological crystalline insulator

We have investigated spin reorientation phenomena and interaction driven effects under the presence of applied strains on the (001) surface of Pb$_{1-x}$Sn$_x$(Te, Se) topological crystalline insulators, which host multiple Dirac cones. Our analysis is based on a four-band $k\cdot p$ model, which captures the spin and orbital textures of the surface states at low energies around the $\bar{X}$ and $\bar{Y}$ points, including the Lifshitz transition. Even without breaking the time-reversal symmetry, we find that certain strains which break the mirror symmetry can induce hedgehog-like spin texture associated with gap formation at the Dirac points. The Chern number of the gapped surface ground state is shown to be tunable through the interplay of strains and a perpendicular Zeeman field. We also consider effects of strain in the presence of interactions in driving competing orders, and obtain the associated phase diagram at the mean-field level. Potential applications of our results for low power consuming electronics are discussed.

Hedgehog spin texture and Berry’s phase tuning in a magnetic topological insulator

Understanding and control of spin degrees of freedom on the surfaces of topological materials are key to future applications as well as for realizing novel physics such as the axion electrodynamics associated with time-reversal (TR) symmetry breaking on the surface. We experimentally demonstrate magnetically induced spin reorientation phenomena simultaneous with a Dirac-metal to gapped-insulator transition on the surfaces of manganese-doped Bi2Se3 thin films. The resulting electronic groundstate exhibits unique hedgehog-like spin textures at low energies, which directly demonstrate the mechanics of TR symmetry breaking on the surface. We further show that an insulating gap induced by quantum tunnelling between surfaces exhibits spin texture modulation at low energies but respects TR invariance. These spin phenomena and the control of their Fermi surface geometrical phase first demonstrated in our experiments pave the way for the future realization of many predicted exotic magnetic phenomena of topological origin.

Mössbauer and calorimetric studies of spin reorientation processes in Er2−xPrxFe14C

The Er2−xPrxFe14C (x = 0.25, 0.5) poly crystalline compounds have been synthesized and investigated by means of X-ray diffraction, 57Fe Mössbauer spectroscopy and Differential Scanning Calorimetry (DSC). The influence of carbon on the spin reorientation phenomena with increasing praseodymium content was of special interest in these compounds. Investigations of spin reorientation phenomena were performed by means of 57Fe Mössbauer spectroscopy with a narrow step temperature scanning in the neighborhood of the spin reorientation temperature. Obtained Mössbauer spectra were analyzed using a procedure of simultaneous fitting and the transmission integral approach. Consistent description of Mossbauer spectra were obtained. Temperature dependencies of hyperfine interaction parameters and subspectra contributions were derived from fits and the transition temperatures were determined for all the compounds studied. DSC studies revealed weak thermal effect (heat absorption) during the transition process. Heat absorption was detected only for the compound with the lowest content of Pr (x = 0.25). The results obtained with different methods were analyzed and data were compared with those for Er2−xPrxFe14B series. The spin arrangement diagram was constructed.

Magnetic structure studies of ternary borides Er2−xCexFe14B

The ternary borides Er2−xCexFe14B (x=0.25, 1, 1.5and 1.7) have been studied by means of X-ray diffraction, 57Fe Mössbauer spectroscopy and magnetic measurements in order to verify the postulated occurrence of conical arrangement of magnetic moments in the region of high Ce-composition. Character of spin reorientation phenomena was investigated by means of 57Fe Mössbauer spectroscopy in the spin reorientation temperature region for polycrystalline and pseudo-single crystal samples. Obtained Mössbauer spectra were analyzed using a procedure of transmission integral. Consistent description of Mössbauer spectra was obtained. Initial magnetization versus temperature measurements (field cooled and zero-field cooled) allowed to estimate the character and temperature regions of reorientation process. The results that are obtained with different methods were compared. The obtained experimental data do not support the hypothesis of conical arrangement of magnetic moments at low temperatures for the compounds with high Ce-composition. Our results are consistent with the current model of spin reorientation in these compounds as a process where magnetic moments rapidly change their orientation from planar to axial arrangement without intermediate conical states.

Spin arrangement diagrams for Er 2− xR xFe 14B (R = Pr, Gd)

57Fe Mössbauer spectroscopy, DSC, X-ray diffraction and magnetic measurements have been applied to study the polycrystalline Er 2− x Pr x Fe 14B ( x = 0.25, 0.5, 0.75, 1.0, 1.5) and Er 2− x Gd x Fe 14B ( x = 0.5, 1.0, 1.5) compounds. A comparison of results obtained for Pr and Gd-based compounds is presented in this paper. Special emphasis was put on the spin reorientation phenomena (change of spin orientation from planar to axial arrangement) occurring in these series. The spin reorientation in each compound has been investigated mainly by narrow step temperature scanning in the neighborhood of the spin reorientation temperature, T SR. Initial magnetization versus temperature measurements allowed to establish the temperature regions of reorientations and also the Curie temperatures of the compounds. The obtained Mössbauer spectra were analyzed by using a procedure of simultaneous fitting and the transmission integral approach. Consistent fits were obtained, T SR and the composition dependencies of hyperfine interaction parameters were derived from fits for all studied compounds. DSC studies proved that the spin reorientations were accompanied by thermal effects. Transformation enthalpy and T SR were determined from these studies only for compounds in which R = Gd. The T SR obtained with different methods were analyzed and the spin arrangement diagrams for two series were compared.

Experimental studies of spin reorientations inEr2−xPrxFe14B

57Fe Mössbauerspectroscopy, x-ray diffraction and magnetic measurements have been used to study the polycrystallineEr2−xPrxFe14B (x = 0.25,0.5, 0.75, 1.0, 1.5) compounds. Special emphasis was put on the spin reorientation phenomena(change of spin orientation from planar to axial arrangement) occurring in this series. Thespin reorientation in each compound has been investigated mainly by means of narrow steptemperature scanning in the neighbourhood of the spin reorientation temperature,TSR.Initial magnetization versus temperature measurements allowed us to establish thetemperature regions of reorientations and also the Curie temperatures of the compounds.Mössbauer temperature scanning was performed with a step of 2 K in the vicinity ofTSR. The spectra obtained were analysed by using a procedure of simultaneousfitting and the transmission integral approach. Consistent fits were obtained;TSR and the composition dependences of hyperfine interaction parameters were derived from fitsfor all compounds studied.The TSR values obtained with both methods were compared and the spin phase diagram for theseries was constructed.

Structure and magnetic properties of Gd 2Co 17− xCr x (1.17 ≤ x ≤ 3.0) compounds

The structure and magnetic properties of Gd 2Co 17− x Cr x (1.17 ≤ x ≤ 3.0) compounds have been investigated by means of X-ray diffraction (XRD) and magnetization measurements. The powder X-ray diffraction patterns show that all samples crystallize as a single phase with the rhombohedral Th 2Zn 17-type structure. The lattice parameters a and the unit cell volume V increases slightly with increasing Cr content, but the c parameter varies in a less simple way with increasing Cr content. The X-ray diffraction patterns of the magnetically aligned samples show that all compounds investigated have uniaxial anisotropy. Spin reorientation phenomena occur in all of the compounds. The Curie temperature T C, the spin reorientation temperature T sr, the spontaneous magnetization M 0 and the saturation magnetization M s decrease with the increasing Cr content. The anisotropy constant K 1 and the anisotropy field B a of the compounds at room temperature reach a maximum for x = 1.76. The M 0 and M s increase with increasing temperature from 5 K to 300 K. The easy-axis anisotropy of all compounds changes to easy-plane anisotropy at low temperatures and the spin reorientation phenomena are more pronounced for low Cr concentration.

Mössbauer and Magnetometric Studies of Spin Reorientations in Er2-xThxFe14B

The Er2ixThxFe14B (x = 0:5, 1.0, 1.5) polycrystalline compounds have been investigated with 57 Fe Mossbauer spectroscopy in the 50{330 K tem- perature range and magnetometry in the temperature range of 4.2{340 K. Initial magnetization vs. temperature measurements allowed us to establish the temperature regions of reorientations and also the Curie temperatures of the compounds. The spin reorientation phenomena (changes from pla- nar to axial spin arrangements) have been studied extensively by a narrow step temperature Mossbauer scanning in the vicinity of the spin reorienta- tion temperatures. From the analysis of the obtained Mossbauer spectra it was deduced that in the region of transition each subspectrum was split into two Zeeman sextets, which were characterised by difierent hyperflne mag- netic flelds and quadrupole splittings. A consistent way of describing the Mossbauer spectra in the wide range of temperatures was proposed. The composition and temperature dependences of hyperflne interaction param- eters and subspectra contributions were derived from experimental spectra. The transition temperatures were determined for all the compounds studied and the spin phase diagram was constructed.

Crystal structure and spin reorientation transition of Tb1−xYxFe11Mo compounds

The structural and magnetic properties of mixed compounds Tb1−xYxFe11Mo with x = 0–1.0 have been investigated by means of x-ray diffraction and magnetic measurements. The compounds crystallize in the tetragonal ThMn12-type structure with space group I4/mmm. The lattice parameters a, c and the unit-cell volume V vary slightly with the Y content, since the atomic radius of Y is close to that of Tb. The Curie temperature of the compounds increases for x ⩽ 0.1, then decreases with the increase in the Y concentration. Spin reorientation phenomena in the Tb1−xYxFe11Mo compounds have been studied in detail. The room temperature easy-magnetization direction of Tb1−xYxFe11Mo compounds changes from planar to the c-axial with increasing Y concentration. Variation of the anisotropy constants of the Fe-sublattice K1(Fe) (T) with temperature is determined experimentally. By minimizing the magnetocrystalline anisotropy energy, the derived spin reorientation temperature for the Tb1−xYxFe11Mo system shows reasonable agreement with the observations.

Experimental studies of spin reorientations inEr2−xThxFe14B

Er2−xThxFe14B (x = 0.0, 0.5, 1.0, 1.5, 2.0) polycrystalline compounds have been studied with57Fe Mössbauer spectroscopy, differential scanning calorimetry (DSC), magnetic measurements andx-ray diffraction. Special emphasis was put on the spin reorientation phenomena (change ofspin orientation from planar to axial arrangement) occurring in this series when increasingtemperature. The spin reorientation in each compound has been investigated mainly bynarrow step temperature scanning in the vicinity of the spin reorientation temperature,TSR.Initial magnetization versus temperature measurements allowed us to establish thetemperature regions of reorientations and the Curie temperatures of the compounds. Thetwo-stage character of transitions was evidenced.Mössbauer temperature scanning was performed with a step of 2 K in the vicinity ofTSR. The obtained spectra were analysed by using a procedure of simultaneousfitting and the transmission integral approach. Consistent fits were obtained;TSR and the composition dependences of hyperfine interaction parameters were derived from fitsfor all studied compounds.DSC studies proved that the spin reorientations were accompanied by thermal effects for compositionx = 0.5. Transformationenthalpy and TSR were determined from these studies and the two-stage character of the transition wasconfirmed.The TSR obtained with different methods were compared and the spin phase diagram for the serieswas constructed.

Spin reorientation and magnetic anisotropy in Y 2Co 17− xCr x ( x = 1.17–3.0) compounds

Spin reorientation transitions and magnetic anisotropy in Y 2Co 17− x Cr x ( x = 1.17–3.0) compounds have been investigated by means of X-ray diffraction and magnetization measurements. The powder X-ray diffraction patterns show that most samples crystallize as a single phase with the rhombohedral Th 2Zn 17-type structure. However, in the compound Y 2Co 14Cr 3 the Th 2Zn 17 phase coexist with the hexagonal Th 2Ni 17-type phase. The lattice parameters a and c hardly change and the unit cell volume V increases slightly with increasing Cr content. The X-ray diffraction patterns of the aligned powder of the samples have confirmed that at room temperature the compound with x = 1.17 has planar anisotropy, but the compounds with x = 1.76, 2.34 and 3.00 have uniaxial anisotropy. Spin reorientation phenomena occur in all of the compounds. With increasing Cr content, the Curie temperature, the spin reorientation temperature, the spontaneous magnetization, and the anisotropy constant K 2 of the Y 2Co 17− x Cr x ( x = 1.17–3.0) compounds decrease strongly while the anisotropy constant K 1 increases in the range of x from 1.17 to 2.34 and then decreases in the range of x from 2.34 to 3.00.

Spin reorientation studies in Er 2− xGd xFe 14B

57Fe Mössbauer spectroscopy, differential scanning calorimetry (DSC), magnetic measurements and X-ray diffraction have been used to study the polycrystalline Er 2− x Gd x Fe 14B ( x = 0.0, 0.5, 1.0, 1.5) compounds. Special emphasis was put on the spin reorientation phenomena (change of spin orientation from planar to axial arrangement) occurring in this series. The spin reorientation in each compound has been investigated mainly by narrow step temperature scanning in the neighborhood of the spin reorientation temperature, T SR. Initial magnetization versus temperature measurements allowed to establish the temperature regions of reorientations and also the Curie temperatures of the compounds. Mössbauer temperature scanning was performed with a step of 1 K in the vicinity of T SR. The obtained spectra were analyzed by using a procedure of simultaneous fitting, and the transmission integral approach. Consistent fits were obtained, T SR and the composition dependencies of hyperfine interaction parameters were derived from fits for all studied compounds. DSC studies proved that the spin reorientations were accompanied by thermal effects. Transformation enthalpy and T SR were determined from these studies. The T SR obtained with different methods were compared and the spin phase diagram for the series was constructed.

Anomalous behavior of electrical resistivity in NdFe 11 Ti

The electrical resistivity, ϱ, and temperature derivative of resistivity (d/dT) of polycrystalline NdFe11Ti are investigated. The resistivity exhibits an anomalous behavior at about 160 K and 220 K. These anomalies attributed to spin reorientation phenomena originate from two magnetic phase transition. A modified theoretical model for electrical resistivity, ϱ and dϱ/dT, behavior in the spin reorientation temperature (TSR) region is presented. The results suggest that the average magnetic moment at TSR1 ∼ 160 K is aligned along a cone angle and at TSR2 ∼ 220 K along c-axis. The temperature dependence of ac-susceptibility, χac(T), is presented. The results show the existence of the spin reorientation related to a magnetic phase transition. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)