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The magnetic phase diagrams of Nd, Nd _{90}Pr_{10 } and Nd_{75}Pr _{25} have been constructed from observed anomalies in thermal expansion and longitudinal magnetostriction measurements in fields up to 12 T. The magnetic structure in... more
The magnetic phase diagrams of Nd, Nd _{90}Pr_{10 } and Nd_{75}Pr _{25} have been constructed from observed anomalies in thermal expansion and longitudinal magnetostriction measurements in fields up to 12 T. The magnetic structure in different regions of the phase diagrams is deduced with reference to neutron diffraction investigations. For Nd, in zero field, discontinuities at T_ {rm N} =
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Abstract CRYOPAD has been used to study the moment directions in the zero field magnetic structures of the rare-earth metal neodymium. Results taken in the 3- q phase between ≈ 6 K and ≈ 8 K are presented. Here the directions of the... more
Abstract CRYOPAD has been used to study the moment directions in the zero field magnetic structures of the rare-earth metal neodymium. Results taken in the 3- q phase between ≈ 6 K and ≈ 8 K are presented. Here the directions of the moments giving rise to the modulation wave vectors q 1 and q 2 (relating primarily to the moments on the hexagonal sites of the DHCP nuclear structure) stay close to a ∗ as one traverses the phase. This is not the case for the moment giving rise to the third modulation wave vector q 3 (relating primarily to the moments on the cubic sites). At the high-temperature end of the 3- q phase this moment is in the a ∗ – c ∗ plane almost parallel to a ∗ , but with a large c ∗ axis component developing as the temperature is reduced. q 3 is split along c by τ =0.05 τ 001 near 8 K. The τ + satellite is due to a moment in the a ∗ – c ∗ plane with a positive c ∗ axis component whereas the τ − satellite is due to a moment in the a ∗ – c ∗ plane with a negative c ∗ axis component equal in magnitude to that of τ + . This result could not have been obtained without being able to measure the transverse component of polarisation.
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Abstract The cubic Laves-phase compound HoCo 2 orders magnetically at 76 K. Its moment undergoes a reorientation with increasing temperature from 〈110〉 to 〈100〉 in the temperature interval 10 to 17 K. The substitution of Rh for Co does... more
Abstract The cubic Laves-phase compound HoCo 2 orders magnetically at 76 K. Its moment undergoes a reorientation with increasing temperature from 〈110〉 to 〈100〉 in the temperature interval 10 to 17 K. The substitution of Rh for Co does not vary the crystal field parameters to any appreciable extent, but does alter the value of the exchange interaction, so that the series Ho(Co 1− c Rh c ) 2 is particularly suitable for the investigation of the spin reorientation. The results of thermal expansion measurements on these compounds are presented and compared with theoretical investigations. It is shown that a single-ion Hamiltonian used in conjunction with suitably chosen crystal-field and exchange parameters can satisfactorily describe the spin reorientation transition. The ‘s-d’ model is used to determine magnetic and related parameters of the series and is found to account quite well for the changing character of the magnetic phase transition.
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Abstract Thermal expansion and magnetostriction measurements have been made on the cubic Laves-phase alloys Ho(Co1−xRhx)2 in the temperature range 2 to 110 K and in fields up to 7 T. The samples were polycrystalline, with x = 0.00, 0.02,... more
Abstract Thermal expansion and magnetostriction measurements have been made on the cubic Laves-phase alloys Ho(Co1−xRhx)2 in the temperature range 2 to 110 K and in fields up to 7 T. The samples were polycrystalline, with x = 0.00, 0.02, 0.05, 0.08, 0.12, 0.16 and 0.25. Two thermal expansion anomalies are observed at a ferromagnetic transition and a spin-flop transition. The change in temperature and ordering nature of these transitions is reported as a function of Rh concentration. Magnetostriction measurements show a marked variance with Rh concentration and suggest the presence of three new distinct magnetic phases.
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U/Fe and U/Gd multilayers constitute magnetic systems, which can be used to probe the hybridisation of the 5f electrons of uranium with 3d and 4f electrons, respectively. A range of samples with varying layer thicknesses was prepared by... more
U/Fe and U/Gd multilayers constitute magnetic systems, which can be used to probe the hybridisation of the 5f electrons of uranium with 3d and 4f electrons, respectively. A range of samples with varying layer thicknesses was prepared by DC sputtering in a UHV chamber. X-ray and neutron reflectivity and X-ray diffraction were used to characterise the structure of the U/Fe
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SQUID magnetometry and polarised neutron reflectivity measure- ments have been employed to characterise the magnetic properties of U/Fe, U/Co and U/Gd multilayers. The field dependence of the magnetisation was measured at 10K in magnetic... more
SQUID magnetometry and polarised neutron reflectivity measure- ments have been employed to characterise the magnetic properties of U/Fe, U/Co and U/Gd multilayers. The field dependence of the magnetisation was measured at 10K in magnetic fields from -70kOe to 70kOe. A temperature dependent study of the magnetisation evolution was undertaken for a selection of U/Gd samples. PNR was carried out in a field of 4.4kOe for U/Fe and U/Co samples (at room temperature) and for U/Gd samples (at 10K). Magnetic 'dead' layers of � 15ûA were observed for U/Fe and U/Co samples, consistent with a picture of interdif- fused interfaces. A large reduction in the magnetic moment, constant over a wide range of Gd layer thicknesses, was found for the U/Gd system (� 4µB compared with 7.63µB for the bulk metal). This could be understood on the basis of a pinning of Gd moments arising from a column-like growth mechanism of the Gd layers. A study of the effective anisotropy suggests that perpendicu...
X-ray magnetic circular dichroism (XMCD) measurements were performed at the U M4,5 edges for U/Fe , U/Co , U/Ni , and U/Gd multilayers. In the case of the U/Fe system, a significant polarization of the U5f electrons was found, but not for... more
X-ray magnetic circular dichroism (XMCD) measurements were performed at the U M4,5 edges for U/Fe , U/Co , U/Ni , and U/Gd multilayers. In the case of the U/Fe system, a significant polarization of the U5f electrons was found, but not for U/Co or U/Ni multilayers. We ascribe this to a hybridization of U5f and Fe3d states, which overlap in
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Due to their complex nature, an investigation of the zero-field magnetic structures of Nd has been started using CRYOPAD, the ILL zero-field neutron polarimeter available on IN20. Having set the incident polarisation to any desired... more
Due to their complex nature, an investigation of the zero-field magnetic structures of Nd has been started using CRYOPAD, the ILL zero-field neutron polarimeter available on IN20. Having set the incident polarisation to any desired direction, CRYOPAD then analyses the magnitude and direction of the polarisation vector of the scattered beam to a precision of 3° at a given momentum transfer. We have confirmed that the moments in the 2-q phase, which order solely on the hexagonal sites of the DHCP structure, are confined to the basal plane at 11.2 K. This was also found to be the case for the moments at the hexagonal sites at 7.6 K in the 3-q phase. Below 8.3 K, the moments on the cubic sites become ordered and we observe both a c-axis and basal plane component. We observe for the first time that the angle between these moments and the basal plane increases continuously with cooling through the 3-q phase.
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We have carried out magnetic neutron diffraction studies of a single crystal of neodymium at high pressure, using clamp cells on the diffractometer D10 at the Institut Laue - Langevin, Grenoble. The magnetic ordering was investigated at... more
We have carried out magnetic neutron diffraction studies of a single crystal of neodymium at high pressure, using clamp cells on the diffractometer D10 at the Institut Laue - Langevin, Grenoble. The magnetic ordering was investigated at pressures up to 14 kbar in the temperature range 1.4 - 25 K. A number of quite different magnetic phases were observed, including
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We found that in TmCo2 the molecular field does not exceed the critical value necessary to induce long-range magnetic order in the Co d-electron subsystem, which is in contrast to the other heavy RCo2 compounds. Below Tc=3.8 K a... more
We found that in TmCo2 the molecular field does not exceed the critical value necessary to induce long-range magnetic order in the Co d-electron subsystem, which is in contrast to the other heavy RCo2 compounds. Below Tc=3.8 K a first-order magnetic phase transition at 3.4 K exists, which is due to a rearrangement of the Tm 4f magnetic moments. When substituting Tm by Gd long-range magnetic order appears in the Co d subsystem. The onset of the magnetic order in the d-electron subsystem can most clearly be seen from thermal expansion measurements. There is an increasing positive volume anomaly with increasing Gd content below Tc. The estimated magnetostriction constant lambda 111 of TmCo2 is -4.1*10-3, in agreement with the single-ion model. Pronounced discontinuities at Tc are characteristic for the transport properties (resistivity and thermopower) for TmCo2 as well as for the pseudobinary Tm1-xGdxCo2 compounds. At elevated temperatures the physical properties of all these compounds are dominated by spin fluctuations.
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Thermal expansion and magnetostriction measurements are reported for single-crystal UNi2Si2. For magnetic fields up to 15 T applied along the c direction and in the temperature range 2–150 K distinct features and anomalies observed in the... more
Thermal expansion and magnetostriction measurements are reported for single-crystal UNi2Si2. For magnetic fields up to 15 T applied along the c direction and in the temperature range 2–150 K distinct features and anomalies observed in the combined results are used to construct a magnetic phase diagram. The diagram extends that deduced from neutron scattering work at low fields.
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The magnetic properties of U1-xPrxPd3, 0 <= x <= 0.2, have been studied in polycrystalline samples by X-ray diffraction, electrical resistivity, magnetization and susceptibility measurements. In UPd3, we observe clearly only the... more
The magnetic properties of U1-xPrxPd3, 0 <= x <= 0.2, have been studied in polycrystalline samples by X-ray diffraction, electrical resistivity, magnetization and susceptibility measurements. In UPd3, we observe clearly only the quadrupolar transition at 6.8 K, which shifts to 5.6 K for x = 0.01. Reminiscences of this transition are observed in the magnetization of compounds with Pr concentrations lower than 5%. For 0.10 <= x <= 0.2 the compounds are paramagnetic down to 2 K, following a power law behaviour for the low temperature susceptibility. Furthermore, all the samples show a modified Curie-Weiss behaviour above 100 K. In U0.8Pr0.2Pd3 the resistivity is linear with temperature from 4.2 to 80 K, and suggests the appearance of new crystalline electrical field levels. The effects of sample annealing are also discussed.
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... Fawcett of the University of Toronto, was grown at the Ames Laboratory and had a resistance ratio of 88. ... 1. Relative expansivity dl/l along the c-axis for sample # 1 (lower TN) and along the b-and c-axes for sample # 2. The... more
... Fawcett of the University of Toronto, was grown at the Ames Laboratory and had a resistance ratio of 88. ... 1. Relative expansivity dl/l along the c-axis for sample # 1 (lower TN) and along the b-and c-axes for sample # 2. The tic-marks on the vertical axis are separated by 10-for ...
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Research Interests: Engineering, Magnetic Recording, Applied Physics, Synchrotron Radiation, Kondo effect, and 11 moreMathematical Sciences, Applied, Physical sciences, Magnetic Properties, Temperature Dependence, Room Temperature, Heavy Fermion, Directional Asymmetry, Superlattices, Momentum Transfer, and Circular polarization
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... Appl. Phys. 93, 6519 2003 . 9 AM Beesley, MF Thomas, ADF Herring, RCC Ward, MR Wells, S. Langridge, SD Brown, SW Zochowski, L. Bouchenoire, WG Stirling, and GH Lander, J. Phys.: Condens. Matter 16, 8491 2004 . 10 ...