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

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

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

Ferromagnetism and strong magnetic anisotropy of the PbMnBO4 orthoborate single crystals

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.The PbMnBO4 orthoborate single crystals were first grownand their magnetic properties and ferro- magnetic resonance were studied. It was found that the ferromagneticstate below the Curie temperature TC=31K is characterized by the strongmagnetic anisotropy. The significant effective anisotropy fields of PbMnBO4 determine the energy gap in the FMR spectrum, which is extraordinary large for ferromagnets (112GHz at T=4.2 K). It was shown tha tthe 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 permit- tivity was observed in PbMnBO4 at the Curie temperature at which the long-range ferromagnetic orde ris established

Ferromagnetism and strong magnetic anisotropy of the PbMnBO4 orthoborate single crystals

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.The PbMnBO4 orthoborate single crystals were first grownand their magnetic properties and ferro- magnetic resonance were studied. It was found that the ferromagneticstate below the Curie temperature TC=31K is characterized by the strongmagnetic anisotropy. The significant effective anisotropy fields of PbMnBO4 determine the energy gap in the FMR spectrum, which is extraordinary large for ferromagnets (112GHz at T=4.2 K). It was shown tha tthe 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 permit- tivity was observed in PbMnBO4 at the Curie temperature at which the long-range ferromagnetic orde ris established

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

Synthesis of the Orthorhombic Dy1-xHoxMnO3 Single Crystals and Study of Their Magnetic Properties

In this report we prepared for the first time the orthorhombic Dy1-xHoxMnO3 single crystals with x = 0, 0.1, 0.2, 0.3, and 0.4 using the flux technique. The post-growth processing and chemical and structural characterization of the synthesized samples were performed. Also we examined the samples obtained by their magnetic properties and the magnetic anisotropy in wide ranges of temperatures and magnetic fields

Magnetic and thermodynamic properties and spin-flop-driven magnetodielectric response of the antiferromagnetic Pb₂Fe₂Ge₂O₉ single crystals

Orthorhombic Pb2Fe2Ge2O9 antiferromagnetic single crystals have been synthesized by a modified pseudo-flux technique and their magnetic, thermodynamic, and magnetodielectric properties have been investigated. It has been found that, below the Ned temperature (45.2 K), iron moments are arranged in a canted antiferromagnetic structure with a weak ferromagnetic moment parallel to the a axis. According to the specific heat measurement data, the T-N value remains invariable in applied magnetic fields of up to 50 kOe within the experimental accuracy. The magnetic entropy in the investigated crystals attains 2Rln(2S + 1) right above T-N, which is indicative of a purely magnetic nature of the transition. It has been shown that the weak ferromagnetic moment is induced by the interplay between the single-ion anisotropy and antisymmetric Dzyaloshinskii-Moriya exchange interaction, with the latter contribution being dominant. It has been established from the angular dependences of the magnetization in three orthorhombic planes that the symmetries of the magnetic and crystal structure are identical. The magnetodielectric properties of the Pb2Fe2Ge2O9 single crystals have been studied at different mutual orientations of the electric and magnetic fields. The most prominent anomalies have been observed in the vicinity of the spin-flop transition in a magnetic field applied along the c axis