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Register a new userSimultaneous Antiferromagnetic Fe3+ and Nd3+ Ordering in NdFe3(11BO3)4
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By means of magnetic susceptibility and specific heat measurements, x-ray and unpolarised neutron diffraction investigations on powder and single-crystal samples, simultaneous long-range antiferromagnetic Fe and Nd ordering in NdFe3(11BO3)4 with R 3 2 chemical structure has been found at temperatures below TN = 30.5(5) K down to 1.6 K. At temperatures down to 20 K to the propagation vector is khex = [0,0,3/2] and becomes slightly incommensurate at lower temperatures. Symmetry analysis yields magnetic spiral configurations with the magnetic moments oriented parallel to hexagonal basal plane according to the irreducible representations tau_3 in the commensurate case. This is in agreement with the easy directions of magnetisation perpendicular to the c-axis as determined by magnetic susceptibility measurements. At 1.6 K the magnetic Fe moment amounts to 4.9 muB close to the free ion moment of Fe3+. The magnetic Nd3+ moment saturates presumably due to crystal-field effects at 2.7 muB.
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We report the low-temperature coexistence in NdFe3(BO3)4 of an incommensurate magnetic phase with a strained commensurate magnetic phase that is primarily at the surface of the crystal. Increasing the temperature or magnetic field decreases the incommensurability and stabilizes the commensurate magnetic phase above Tic ~14 K or Hic = 0.9 T. A comparison to published studies indicates the onset of longitudinal magnetostriction and electric polarization at the magnetic-field-induced transition, which may arise due to a basal plane spin-flop and canting of the moments along the field direction.
Complex experimental and theoretical study of the magnetic, magnetoelectric, and magnetoelastic properties of neodymium iron borate NdFe3(BO3)4 along various crystallographic directions have been carried out in strong pulsed magnetic fields up to 230 kOe in a temperature range of 4.2-50 K. It has been found that neodymium iron borate, as well as gadolinium iron borate, is a multiferroic. It has much larger (above 3 10^(-4) C/m^2) electric polarization controlled by the magnetic field and giant quadratic magnetoelectric effect. The exchange field between the rare-earth and iron subsystems (~50 kOe) has been determined for the first time from experimental data. The theoretical analysis based on the magnetic symmetry and quantum properties of the Nd ion in the crystal provides an explanation of an unusual behavior of the magnetoelectric and magnetoelastic properties of neodymium iron borate in strong magnetic fields and correlation observed between them.
La2Au2Cd and Ce2Au2Cd were prepared from the elements by reactions in sealed tantalum tubes in a water-cooled sample chamber of an induction furnace. These intermetallics crystallize with the tetragonal Mo2FeB2 type, space group P4/mbm. While La2Au2Cd is Pauli paramagnetic, Ce2Au2Cd shows Curie-Weiss behaviour above 100 K with an experimental magnetic moment of 2.41(2) muB/Ce atom, indicating trivalent cerium. Antiferromagnetic ordering is detected for Ce2Au2Cd at 5.01(2) K and magnetization measurements reveal a metamagnetic transition at 3 K at a critical field of around 20 kOe with a saturation moment of 1.50(2)muB/Ce atom at 80 kOe. The low-temperature heat capacity properties characterize Ce2Au2Cd as a heavy fermion material with an electronic specific heat coefficient (gamma) = 807(5) mJ/mol K2 as compared to La2Au2Cd with gamma = 6(5) mJ/mol K2.
Fe$_{3-x}$GeTe$_2$ is a layered van der Waals magnetic material with a relatively high ordering temperature and large anisotropy. While most studies have concluded the interlayer ordering to be ferromagnetic, there have also been reports of interlayer antiferromagnetism in Fe$_{3-x}$GeTe$_2$. Here, we investigate the interlayer magnetic ordering by neutron diffraction experiments, scanning tunneling microscopy (STM) and spin-polarized STM measurements, density functional theory plus U calculations and STM simulations. We conclude that the layers of Fe$_{3-x}$GeTe$_2$ are coupled ferromagnetically and that in order to capture the magnetic and electronic properties of Fe$_{3-x}$GeTe$_2$ within density functional theory, Hubbard U corrections need to be taken into account.
Antiferromagnetic order at $T_{mathrm{N}} = 23$ K has been identified in Mn(III)F(salen), salen = H$_{14}$C$_{16}$N$_2$O$_2$, an $S = 2$ linear-chain system. Using single crystals, specific heat studies performed in magnetic fields up to 9 T revealed the presence of a field-independent cusp at the same temperature where $^1$H NMR studies conducted at 42 MHz observed dramatic changes in the spin-lattice relaxation time, $T_1$, and in the linewidths. Neutron powder diffraction performed on a randomly-oriented, as-grown, deuterated (12 of 14 H replaced by d) sample of 2.2 g at 10 K and 100 K did not resolve the magnetic ordering, while low-field (less than 0.1 T) magnetic susceptibility studies of single crystals and randomly-arranged microcrystalline samples reveal subtle features associated with the transition. Ensemble these data suggest a magnetic signature previously detected at 3.8 T for temperatures below nominally 500 mK is a spin-flop field of small net moments arising from alternating subsets of three Mn spins along the chains.
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