56 research outputs found
Magnetic structure of the field-induced multiferroic GdFe3(BO3)4
We report a magnetic x-ray scattering study of the field-induced multiferroic
GdFe3(BO3)4. Resonant x-ray magnetic scattering at the Gd LII,III edges
indicates that the Gd moments order at TN ~ 37 K. The magnetic structure is
incommensurate below TN, with the incommensurability decreasing monotonically
with decreasing temperature until a transition to a commensurate magnetic phase
is observed at T ~ 10 K. Both the Gd and Fe moments undergo a spin
reorientation transition at TSR ~ 9 K such that the moments are oriented along
the crystallographic c axis at low temperatures. With magnetic field applied
along the a axis, our measurements suggest that the field-induced polarization
phase has a commensurate magnetic structure with Gd moments rotated ~45 degrees
toward the basal plane, which is similar to the magnetic structure of the Gd
subsystem observed in zero field between 9 and 10 K, and the Fe subsystem has a
ferromagnetic component in the basal plane.Comment: 27 pages, 7 figures, to appear in Phys. Rev.
Magnetoelectric Effect and Spontaneous Polarization in HoFe(BO) and HoNdFe(BO)
The thermodynamic, magnetic, dielectric, and magnetoelectric properties of
HoFe(BO) and HoNdFe(BO) are
investigated. Both compounds show a second order Ne\'{e}l transition above 30 K
and a first order spin reorientation transition below 10 K.
HoFe(BO) develops a spontaneous electrical polarization below the
Ne\'{e}l temperature (T) which is diminished in external magnetic fields.
No magnetoelectric effect could be observed in HoFe(BO). In
contrast, the solid solution HoNdFe(BO) exhibits
both, a spontaneous polarization below T and a magnetoelectric effect at
higher fields that extends to high temperatures. The superposition of
spontaneous polarization, induced by the internal magnetic field in the ordered
state, and the magnetoelectric polarizations due to the external field results
in a complex behavior of the total polarization measured as a function of
temperature and field.Comment: 12 pages, 15 figure
Magnetic and thermodynamic properties and spin-flop-driven magnetodielectric response of the antiferromagnetic Pb2Fe2Ge2O9 single crystals
ANTIFERROMAGNETIC RESONANCE IN CRYSTALS OF THE FAMILY PrXY1-XFe3(BO3)4 WITH ANGULAR MAGNETIC STRUCTURE
With diamagnetic dilution of the PrFe3(BO3)4 subsystem with nonmagnetic yttrium, the anisotropic contribution of the Pr3+ subsystem decreases; in the concentration range x = 0.67-0.45, a transition from the LO to the LP magnetic structure occurs through the formation of angular magnetic structure
Ferromagnetism and strong magnetic anisotropy of the PbMnBO<inf>4</inf> orthoborate single crystals
© 2016 Elsevier B.V. All rights reserved.The PbMnBO4 orthoborate single crystals were first grown and their magnetic properties and ferromagnetic resonance were studied. It was found that the ferromagnetic state below the Curie temperature TC=31 K is characterized by the strong magnetic anisotropy. The significant effective anisotropy fields of PbMnBO4 determine the energy gap in the FMR spectrum, which is extraordinary large for ferromagnets (112 GHz at T=4.2 K). It was shown that the static Jahn-Teller effect characteristic of the Mn3+ ion leads to both the ferromagnetic ordering and the strong magnetic anisotropy in the crystal. In the strong external magnetic field the induced ferromagnetic ordering is retained in the crystal above the Curie temperature up to the temperatures multiply higher than TC. A weak anomaly of the dielectric permittivity was observed in PbMnBO4 at the Curie temperature at which the long-range ferromagnetic order is established
Forming a ferrimagnetic-like structure in the PbMn1−xFexBO4 (x ≈ 0.1) single crystal upon partial substitution
Forming a ferrimagnetic-like structure in the PbMn1−xFexBO4 (x≈0.1) single crystal upon partial substitution
The PbMn1−xFexBO4 (x≈0.1) orthoborate single crystals have been grown for the first time by spontaneous crystallization and their magnetic and resonance
properties and specific heat have been examined. It has been established that partial substitution of iron ions for manganese ones leads to an increase in the Curie
temperature to 34.2 K from its value of 30.3 K in the unsubstituted crystal, enhances the magnetic anisotropy, and reduces the saturation magnetization. The
magnetization drop is explained in the framework of the model of a ferrimagnetic-like structure, in which the magnetic moments of iron and manganese ions form
ferromagnetic subsystems coupled by the antiferromagnetic exchange.
It has been found that under magnetization along the rhombic b axis the magnetic moments switch stepwise to the magnetic field direction in a certain critical
field. The spin-reorientation transition is the first-order one. This feature of the crystal magnetization does not allow the experimental ferromagnetic resonance
frequency-field dependence for the rhombic b axis to be described using the calculation for a simple rhombic ferromagnet. It has been established that the increase in
the magnetic anisotropy of the crystal upon substitution leads to an increase in the energy gap in the ferromagnetic resonance spectrum to 121.5 GHz at T=4.2 K
Peculiarities of a magnetic transition in a quasi-one-dimensional ferromagnet PbMnBO4
Near the Curie temperature TC=30.3 K, the temperature dependences of the magnetization and heat capacity of a single-crystal ferromagnet PbMnBO4 in the magnetic fields of 1, 3, 10 and 30 kOe are studied. In the strong magnetic fields, both the magnetic contribution to the specific heat and the nonlinearity of the field dependences of the magnetization are maintained up to the temperatures exceeding TC more than twice. It is assumed that in PbMnBO4 the difference between TC, the paramagnetic Curie temperature θ=49 K and the broad temperature region above TC where the magnetic contribution to the specific heat is significant is due to the quasi-one-dimensional character of the magnetic structure of this ferromagnet. Using both the estimation of TC from the Ginzburg-Landau field theory and the θ value, the total exchange interaction parameters 2J≈40.4 K (intrachain) and z′J′≈8.8 K (interchain) are determined, with z′=4 being the number of neighboring chains. The estimation shows that the Ginzburg-Landau field theory describing the quasi-one-dimensional behavior of PbMnBO4 is well applicable in the temperature range from to T=S2J≈80 K. Above this temperature, the mean field approximation with the exchange parameter λθ based on the paramagnetic Curie temperature θ describes well the experimental temperature dependences of the magnetization in the strong magnetic field and the specific heat is determined by the lattice contribution
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