•The HoFeO3 has a rich phase diagram in an external magnetic field, which includes 8 magnetic phases.•The richness of phase is the result of balance of exchange interactions and the external ...field.•Some of the phases are suppressed by the magnetic field.
Neutron diffraction studies of HoFeO3 single crystals were performed under external magnetic fields. The interplay between the external magnetic fields, Dzyaloshinsky-Moria antisymmetric exchange, isotropic exchange interactions between Fe and Ho sublattices and within the Fe sublattice provides a rich magnetic phase diagram. As the result of the balance of exchange interactions inside the crystal and external magnetic fields, we found 8 different magnetic phases, induced or suppressed dependent on the external field.
•Exchange parameters between nearest neighbors for Fe3+ in TbFeO3 were obtained.•The magnetic phase diagram for YbFeO3 was obtained and discussed.•The obtained temperature dependences of the energy ...gap, well demonstrate the influence of anisotropy.
Investigations of the orthoferrites TbFeO3 and YbFeO3 were performed by neutron inelastic scattering and neutron single crystal diffraction in magnetic fields. The low temperature evolution of energy gaps was explored for both compounds and considered from the point of view of changes of rare earth ion anisotropy. Exchange parameters between nearest neighbors for Fe3+ in TbFeO3 were obtained. The magnetic phase diagram for YbFeO3 was obtained and discussed as a result of the energy balance between Heisenberg exchange interactions, Dzyaloshinsky-Moriya interaction, anisotropy and external magnetic field.
The magnetostriction of HoMnO3 hexagonal single crystals was investigated for a wide range of applied magnetic fields with strengths up to H=14T for all possible combinations of magnetic field ...orientation H and magnetostriction ΔL/L. The anomalies found in the magnetostriction measurements of HoMnO3 correlate well with the phase diagram of these compounds. For the first time the measurements of magnetostriction of HoMnO3 single crystal were made in all five possible configurations.
The crystal structure and magnetic properties investigations of holmium orthoferrite compound HoFeO
3
were performed in temperature range 7–300 K. Obtained XRD data confirm that HoFeO
3
retains the ...orthorhombic perovskite structure of
Pbnm
space group. The crystal electric field (CEF) parameters of Ho
3+
ion subsystem has been revealed numerically on the base of point charge model in the same temperature range. By this set of parameters CEF the splitting of Ho
3+
energy levels was calculated and their temperature evolution was obtained. Modelling of isothermal magnetization
M
(
H
) with obtained set of parameters was carried out. Ho
3+
single ion anisotropy due to CEF effects was demonstrated. Bulk magnetization evaluated from CEF was compared to experimental data.
In this paper, we present a comprehensive study of magnetic dynamics in the rare-earth orthoferrite YbFeO3 at temperatures below and above the spin-reorientation (SR) transition TSR=7.6K, in magnetic ...fields applied along the a,b, and c axes. Using single-crystal inelastic neutron scattering, we observed that the spectrum of magnetic excitations consists of two collective modes well separated in energy: 3D gapped magnons with a bandwidth of ∼60meV, associated with the antiferromagnetically (AFM) ordered Fe subsystem, and quasi-1D AFM fluctuations of ∼1meV within the Yb subsystem, with no hybridization of those modes. The spin dynamics of the Fe subsystem changes very little through the SR transition and could be well described in the frame of semiclassical linear spin-wave theory. On the other hand, the rotation of the net moment of the Fe subsystem at TSR drastically changes the excitation spectrum of the Yb subsystem, inducing the transition between two regimes with magnon and spinonlike fluctuations. At T<TSR, the Yb spin chains have a well defined field-induced ferromagnetic (FM) ground state, and the spectrum consists of a sharp single-magnon mode, a two-magnon bound state, and a two-magnon continuum, whereas at T>TSR only a gapped broad spinonlike continuum dominates the spectrum. In this work we show that a weak quasi-1D coupling within the Yb subsystem JYb-Yb, mainly neglected in previous studies, creates unusual quantum spin dynamics on the low-energy scales. The results of our work may stimulate further experimental search for similar compounds with several magnetic subsystems and energy scales, where low-energy fluctuations and underlying physics could be “hidden” by a dominating interaction.
•Strong mutual influence of manganese and rare earth systems in DyMnO3.•Specific hysteretic behavior of the magnetic order.•Two propagation vectors for Dy magnetic subsystem simultaneously.
...Structural and magnetic properties of single crystals of DyMnO3 were investigated by neutron diffraction in order to study the peculiarities of 3d-4f interactions in this compound. Precise magnetic order and its detailed temperature evolution were determined using single crystal neutron diffraction. Elliptical cycloid on manganese subsystem below TCh = 19 K was confirmed, with temperature decrease the elipticity of the Mn magnetic structure reduces significantly, creating almost circular cycloid. Temperature evolution of the magnetic structure demonstrate specific hysteretic behavior. The results show a complex interplay between transition metal and rare earth magnetic sublattices leading to so-called “Mn- controlled” and “Dy- controlled” magnetic states. The strong and complicate 3d-4f interaction leads to the unusual very slow magnetic structure relaxation.
We report on the low-temperature magnetic properties of the DyScO3 perovskite, which were characterized by means of single crystal and powder neutron scattering, and by magnetization measurements. ...Below TN=3.15 K, Dy3+ moments form an antiferromagnetic structure with an easy axis of magnetization lying in the ab plane. The magnetic moments are inclined at an angle of ∼±28∘ to the b axis. We show that the ground-state Kramers doublet of Dy3+ is made up of primarily |±15/2〉 eigenvectors and well separated by a crystal field from the first excited state at E1=24.9 meV. This leads to an extreme Ising single-ion anisotropy, M⊥/M∥∼0.05. The transverse magnetic fluctuations, which are proportional to M⊥2/M∥2, are suppressed, and only moment fluctuations along the local Ising direction are allowed. We also found that the Dy-Dy dipolar interactions along the crystallographic c axis are two to four times larger than in-plane interactions.
Effect of substitution Dy by Ho on the magneto-electric behavior of the compound Dy0.8Ho0.2MnO3 was investigated by the different methods of polarized and classical neutron diffraction and ...macroscopic methods. It is shown that substitution by Ho of 20% on the position of Dy do not change overall crystal symmetry of compound. It remains of Pbnm type down to the very low temperatures. Magnetic ordering, its temperature and field evolution was determined by the use of single crystal neutron diffraction and magnetization measurements. Chiral type of magnetic structure on Mn subsystem is confirmed below Tc ≈ 16 K. Using polarized neutron diffraction the 3-component character of rare earth magnetic ordering in Dy0.8Ho0.2MnO3 in contrast to DyMnO3 could be revealed. It was shown that doping by 20% Ho suppresses the spontaneous rare-earth ordering with its own propagation vector and provides the situation when two magnetic subsystems, manganese and rare earth ones have a coherent incommensurate spatial propagation. The influence of the external electric field on the magnetic chirality could be directly evidenced, proving strong magneto-electric coupling in multiferroic phase. The study of the electric polarization under similar temperatures and fields on the same samples provides the direct correlation between the results of the microscopic and macroscopic investigations.
We investigate the magnetic dynamics of the orthorhombic perovskite TmFeO3 at low temperatures, below the spin reorientation transition at TSR≈80 K, by means of time-of-flight neutron spectroscopy. ...We find that the magnetic excitation spectrum combines two emergent collective modes associated with different magnetic sublattices. The Fe subsystem orders below TN∼632 K into a canted antiferromagnetic structure and exhibits sharp, high-energy magnon excitations. We describe them using linear spin-wave theory, and reveal a pronounced anisotropy between in- and out-of-plane exchange interactions, which was mainly neglected in previous reports on the spin dynamics in orthoferrites. At lower energies, we find two crystalline electrical field (CEF) excitations of Tm3+ ions at energies of ∼2 and 5 meV. In contrast to the sister compound YbFeO3, where the Yb3+ ions form quasi-one-dimensional chains along the c axis, the Tm excitations show dispersion along both directions in the (0KL) scattering plane. Analysis of the neutron scattering polarization factor reveals a longitudinal polarization of the 2 meV excitation. To evaluate the effect of the CEF on the Tm3+ ions, we perform point-charge model calculations, and their results quantitatively capture the main features of Tm single-ion physics, such as energies, intensities, and polarization of the CEF transitions, and the type of magnetic anisotropy.
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