Multiple magnetic transitions inEr2Ni2Pb

IEEE Transactions on Magnetics, 2000

The effect of combined presence of iron and nickel has been studied in rapidly quenched amorphous (Fe-Ni) 81 Nb 7 B 12 system with the ratio of Fe/Ni = 2 1 and 1/2 in as-quenched state and after annealing. Field dependencies of magnetostriction as well as the values of saturation magnetostriction were correlated with the evolution of nanocrystalline structure in amorphous matrix in the temperature range from 700 to 800 K and after complete crystallization above 900 K. Intervals of stability and transformation regions were determined from temperature dependencies of electrical resistivity. The structure after annealing at selected temperatures was identified by X-ray diffraction (XRD), transmission electron microscopy (TEM), and electron diffraction. Mössbauer spectroscopy was used only as a complementary method to demonstrate the behaviour and development of the paramagnetic (FeNi) 23 B 6 phase from the original as-quenched structure. Mössbauer and magnetostriction measurements were performed at room temperature. The observed field dependencies of magnetostriction are a combination of magnetostrictions of ferromagnetic and paramagnetic phases formed during the transformation process, namely, the nanocrystalline cubic Fe-Ni phases and face-centered cubic (fcc)-type structure (FeNi) 23 B 6 , as identified from the structure analyses. The transition from purely ferromagnetic to partially paramagnetic state is well observed in the evolution of Mössbauer spectra evolution. Different ratios of both ferromagnetic components Fe and Ni lead to a change of the structure of the nanocrystalline phases and thus also to a change in the magnetic behavior of the system.

Physical Review B

Journal of Applied Physics, 2008

The metamagnetic transitions in single-crystal ErNi2B2C have been studied at 1.9 K with a Quantum Design torque magnetometer. The critical fields of the transitions depend crucially on the angle between applied field and the easy axis [100]. Torque measurements have been made while changing angular direction of the magnetic field (parallel to basal tetragonal ab-planes) in a wide angular range (more than two quadrants). Sequences of metamagnetic transitions with increasing field are found to be different for the magnetic field along (or close enough to) the easy [100] axis from that near the hard [110] axis. The study have revealed new metamagnetic states in ErNi2B2C which were not apparent in previous longitudinal-magnetization and neutron studies.

2022

EuMnSb$_2$ is a candidate topological material which can be tuned towards a Weyl semimetal, but there are differing reports for its antiferromagnetic (AFM) phases. The coupling of bands dominated by pure Sb layers hosting topological fermions to Mn and Eu magnetic states provides a potential path to tune the topological properties. We present a detailed analysis of the magnetic structure on three AFM phases based on single-crystal neutron diffraction, magnetization, and heat capacity data as well as polycrystalline $^{151}$Eu Mössbauer data. The Mn magnetic sublattice orders into a C-type AFM structure below $323(1)$~K with the ordered Mn magnetic moment $\mu_{\text{Mn}}$ lying perpendicular to the layers. AFM ordering of the Eu sublattice occurs below $23(1)$~K with the ordered Eu magnetic moment $\mu_{\text{Eu}}$ canted away from the layer normal and $\mu_{\text{Mn}}$ retaining its higher-temperature order. $\mu_{\text{Eu}}$ is ferromagnetically aligned within each Eu layer but exhibits a complicated AFM layer stacking. Both of these higher-temperature phases are described by magnetic space group (MSG) $Pn^{\prime}m^{\prime}a^{\prime}$ with the chemical and magnetic unit cells having the same dimensions. Cooling below $=9(1)$~K reveals a third AFM phase where $\mu_{\text{Mn}}$ remains unchanged but $\mu_{\text{Eu}}$ develops an additional in-plane canting. This phase has MSG $P11\frac{2_1}{a^{\prime}}$. We additionally find evidence of short-range magnetic correlations associated with the Eu between $12~\text{K} \lesssim T \lesssim 30~\text{K}$. Using the determined magnetic structures, we postulate the signs of nearest-neighbor intralayer and interlayer exchange constants and the magnetic anisotropy within a general Heisenberg-model. We then discuss implications of the various AFM states in EuMnSb$_2$ and its topological properties.

Physical Review B, 1997

Neutron-diffraction measurements have been carried out to investigate the crystal structure, magnetic structures, and magnetic phase transitions in RNi 2 B 2 C (Rϭ Y, Ce, Pr, Nd, Tb, Dy, Ho, Er, Tm, and Yb͒. The materials that order magnetically exhibit a wide variety of both commensurate and incommensurate magnetic structures, which argues strongly that the dominant exchange interactions are of the indirect Ruderman-Kittel-Kasuya-Yosida type. The Nd system exhibits a commensurate antiferromagnetic ordering at 4.8 K, with wave vector ␦ϭ(1/2,0,1/2) and moment direction along a ͑or equivalently with ␦ϭ(0,1/2,1/2) and moment direction along b in this tetragonal system͒. For Dy (T N ϭ10.6 K), Pr (T N ϭ4.0 K), and the low-temperature phase of Ho, the magnetic structure is also a commensurate antiferromagnet that consists of ferromagnetic sheets of rare-earth moments in the a-b plane, with the sheets coupled antiferromagnetically along the c axis ͓␦ϭ(0,0,1)͔. Pr is not superconducting, while for Dy (T c ϭ6 K) and Ho (T c ϭ8 K) this magnetic order coexists with superconductivity. For Ho, though, the magnetic state that initially forms at T N Ϸ8.5 K is an incommensurate spiral antiferromagnetic state along the c axis in which the direction of these ferromagnetic sheets are rotated in the a-b plane by ϳ17°from their low-temperature antiparallel configuration ͓␦ϭ(0,0,0.91)͔. The intensity for this spiral state reaches a maximum near the reentrant superconducting transition (ϳ5 K); the spiral state then collapses at lower temperature in favor of the commensurate antiferromagnetic state. An incommensurate a-axis modulation, with ␦ϭ(0.55,0,0), is also observed above the spiral-antiferromagnetic transition, but it exists over a narrower temperature range than the spiral state, and also collapses near the reentrant superconducting transition. The Er system forms an incommensurate, transversely polarized spin-density wave ͑SDW͒ state at T N ϭ6.8 K, with ␦ϭ(0.553,0,0) and moment direction along b ͑or with ␦ along b and the moment direction along a). The SDW squares up at low T, and coexists with the superconducting state (T c ϭ11 K) over the full temperature range where magnetic order is present. Tb, which does not superconduct, orders with a very similar wave vector, but the SDW is longitudinally polarized in this case and again squares up at low T. Tm orders at T N ϭ1.5 K in a transversely polarized SDW state, but with the moments along the c axis and ␦ϭ(0.093,0.093,0). This state is coexistent with superconductivity (T c ϭ11 K). No significant magnetic moment is found to develop on the Ni site in any of the materials, and there is no magnetic ordering of any kind in the Y, Yb, or Ce materials. Profile refinements have also been carried out on these same samples to investigate the systematics of the crystallography, and the crystal structure is I4/mmm over the full range of compositions and temperatures investigated. The area of the a-b plane and the volume of the unit cell both decrease smoothly with either decreasing lanthanide radius or decreasing temperature, but the strong boron-carbon and nickel-carbon bonding then forces the c axis to expand.