Low-temperature Magnetostriction Research Articles

Strong magnetoelastic effect in CeCo1−xFexSi as Néel order is suppressed

A very strong magnetoelastic effect in the CeCo$_{1-x}$Fe$_{x}$Si alloys is reported. The strength of the magnetostrictive effect can be tuned upon changing $x$. The moderate low-temperature linear magnetostriction observed at low Fe concentrations becomes very large ($\frac {\Delta L}{L} \left(16 T,2 K\right) =$ 3$\times$10$^{-3}$) around the critical concentration ($x_c \approx$ 0.23) at which the long-range antiferromagnetic order vanishes. Upon increasing doping through the non-magnetic region ($x > x_c$), the magnetostriction strength gradually weakens again. Remarkably the low-temperature magnetostriction at the critical concentration shows a pronounced $S$-like shape (centered at $B_m \sim$ 6 T) resembling other well-known Ce-based metamagnetic systems like CeRu$_2$Si$_2$ and CeTiGe. Unlike what is observed in these compounds, however, the field dependence of the magnetization shows only a minor upturn around $B_m$ vaguely resembling a metamagnetic behavior. The subtle interplay between magnetic order and the Kondo screening seems to originate an enhanced valence susceptibility slightly changing the Ce ions valence, ultimately triggering the large magnetostriction observed around the critical concentration.

Low-temperature magnetostriction and distortions in the rare-earth Laves phases

The effects of partial substitution of dysprosium in Tb0.2Dy0.8Co2 by terbium and gadolinium on the structure and magnetic properties have been studied. Two compositions, Tb0.3Dy0.7Co2 and Tb0.2Dy0.7Gd0.1Co2 have been synthesized. Their crystal structure, in contrast to the structure of the original compound, has both tetragonal distortions and rhombohedral distortions at lower temperatures. Anomalies of magnetostriction and magnetocaloric effect near the observed magnetic phase transitions have been studied. The sign-alternating temperature dependences of the longitudinal and transverse magnetostrictions associated with various types of crystal structure distortions of the alloys are revealed.

Spin reorientation and giant low-temperature magnetostriction of polycrystalline NdFe1.9 compound

The spin reorientation and magnetostriction of polycrystalline NdFe1.9 cubic Laves phase compound were investigated. A prominent transition from tetragonal symmetry to orthorhombic symmetry in NdFe1.9 compound was determined by X-ray crystallographic study. Meanwhile, a large spontaneous magnetostriction λ111 of ∼3100 ppm was detected at 15 K, which is larger than the theoretical value of 2000 ppm predicted by single-ion model. NdFe1.9 exhibits larger low-field magnetostriction than PrFe1.9 and TbFe1.9 at 5 K in the magnetic field range of H ≤ 13 kOe, which makes it a promising material for low-temperature applications. The present work might be helpful to discover inexpensive Nd-based high-performance magnetostrictive and even magnetoelectric materials for low-temperature applications.

Magnetostriction of the spin-ice system Yb2Ti2O7

Low temperature magnetostriction effects have been studied at Yb2Ti2O7 which is characterized by a geometric magnetic frustration. The experimental finding and the developed theory suggest that Yb2Ti2O7 is a quantum spin ice. Most of the magnetoelastic effects can be explained by an exchange striction model. The external magnetic field together with the temperature govern the transition between the collective paramagnetic behavior of the classical spin ice and the magnetically ordered state.

Anisotropic thermal expansion and magnetostriction ofYNi2B2C single crystals

We present results of anisotropic thermal expansion and low temperature magnetostriction measurementson YNi2B2C single crystals grown by high temperature flux and floating zone techniques. Quantumoscillations of magnetostriction were observed at low temperatures for starting at fields significantly belowHc2 (H<0.7Hc2). Large irreversible, longitudinal magnetostriction was seen in both in-plane and along thec axis directions of the applied magnetic field in the mixedsuperconducting state. Anisotropic uniaxial pressure dependences ofTc were evaluated using results of zero field, thermal expansion measurements.

Magnetism in a UNi2/3Rh1/3Al single crystal

We report a magnetization, magnetostriction, electrical resistivity, specific heat and neutron scattering study of a UNi2/3Rh1/3Al single crystal, a solid solution of an antiferromagnet UNiAl and a ferromagnet URhAl. The huge uniaxial magnetic anisotropy confining the principal magnetic response to the c axis in the parent compounds persists also for the solid solution. The magnetization curve at 1.6 K has a pronounced S shape with an inflection at 12 T. The temperature dependence of magnetic susceptibility exhibits a maximum around 10 K and is magnetic history dependent at lower temperatures where the resistivity increases linearly with decreasing temperature. The low-temperature ρ(T) anomaly is removed in a magnetic field applied along c, which yields a large negative magnetoresistance amounting to m46 zin 14T (at 2 K). The C/T values exhibit a minimum around 12 K and below 8 K they become nearly constant (about 250 mJ mol−1 K−2), which is strongly affected by magnetic fields. Neutron scattering data confirm a non-magnetic ground state of UNi2/3Rh1/3Al. The bulk properties at low temperatures are tentatively attributed to the freezing of U magnetic moments with antiferromagnetic correlations. The additional intensities detected on top of nuclear reflections in neutron diffraction in a magnetic field applied along c are found to be proportional to the field-induced magnetization, which reflects field-induced ferromagnetic coupling of U magnetic moments. This scenario is corroborated also by finding low-temperature magnetostriction data that also scale with the square of magnetization.

Low-temperature magnetostriction of magnets and superconductors (Preface)

First Page

Low temperature magnetostriction of amorphous Fe85B15 ribbons

In this work we present measurements of the low temperature behavior of the magnetostriction of amorphous Fe 85 B 15 samples that were produced by planar flow casting. For these low temperature measurements we developed a new system in order to characterize amorphous or nanocrystalline ribbons in a temperature range between 2 K and 300 K. With the system the low temperature dependence of magnetostriction can be measured by the SAMR-(Small Angle Magnetization Rotation) method which exhibits a high sensitivity. Additionally magnetic measurements like hysteresis loop, initial susceptibility and pinning field were performed with the same equipment simultaneously on the same piece of ribbon. The magnetostriction and the magnetization data of the Fe 85 B 15 sample were used for analyzing the temperature dependence of magnetostriction in the low temperature range. From scaling laws between the magnetostriction and the saturation magnetization information about the physical mechanism of magnetostriction can be obtained. The temperature dependence of coercivity H c will also be analyzed by various models. From the temperature dependence of the magnetization, which follows the Bloch T 3/2 law, the spin wave stiffness constant can be estimated.

High-field magnetostriction in the pseudo-metamagnetic heavy-fermion system CeRu2Si2

Low-temperature magnetostriction experiments have been performed on CeRu2Si2 single crystals in magnetic fields up to 15T. WhenH is applied parallel to the tetragonalc-axis, a very large expansion is observed in all lattice directions. A pronounced anomaly occurs at a field close to the “metamagnetic” threshold. The results are discussed with use of thermodynamic relations and support a very simple scaling behavior for the pressure dependence of the magnetization.

Low temperature magnetostriction and magnetization of RE x Y1?x Pd3-alloys

Low temperature magnetostriction and magnetization measurements are reported for the series of RE x Y1−xPd3 alloys and for some REPd3 compounds. The magnetostriction per Rare Earth ion is nearly independent of concentration and conserves volume at low fields. In both the alloys and compounds with the heavy Rare Earths and with Nd the magnetostriction tends to saturate at high fields together with the magnetization. The saturated quadrupolar magnetostriction as extracted from these data via the Callen projection, is of order a few times 10−3 per Rare Earth ion. Sign and magnitude of this quadrupole do not correlate with the Stevens factor. The results are discussed in terms of aspherical screening of the nuclear charge from the outer valence electrons by the intervening 4f charge distribution.

Magnetostriction in Single-Crystal and Polycrystalline Silver Doped with Rare Earths

We have measured the low-temperature magnetostriction in silver-rare-earth single-crystal and polycrystaline alloys at rare-earth concentrations of about 0.5%. For each monocrystal, the $〈100〉$ and $〈111〉$ magnetostrictions are of the same sign and follow the sign of the Stevens factor $\ensuremath{\alpha}$. Unannealed polycrystals show quite different behavior from the monocrystals.

Magnetostriction of rare-earth iron garnets at low temperatures

Results are given of low-temperature magnetostriction measurements on single crystals of Yb- and Tb-doped yttrium iron garnet. From these data, the stress contribution to the magnetocrystalline anisotropy is calculated.