Spin fluctuations in manganese intermetallics
Spin fluctuations in manganese intermetallics
Magnetic ground states and dynamics in manganese systems have been investigated for two different types of structure, the binary β-Mn1-xMx and ternary RMn4Al8 intermetallics where M represents cobalt or ruthenium and R is a rare earth element/yttrium/scandium.
For β-Mn alloys containing cobalt impunities, a static ground state of spin glass-like character has been stabilised for concentrations above 5% Co; there is an absence however of long range order in these systems, up to the highest measured concentration of 25at.% Co. The β-Mn1-xRux alloys enter a spin glass-type state for all measured concentrations (above x = 0.03), in conjunction with a higher-temperature transition to a long range antiferromagnetically ordered state for x = 0.12, co-existent with the spin glass phase. These findings are evidenced by peaks in the muon spin relaxation rate, with a characteristic stretched exponential relaxation function observed below the spin glass transition temperature. Further support is provided by susceptibility and polarized neutron measurements. Clear magnetic Bragg peaks in neutron powder diffraction data, in addition to specific heat anomalies, confirm the presence of the long-range ordered state in the ruthenium alloys. Neutron lineshapes in a number of samples of both series may also imply Non-Fermi liquid scaling.
These results are of particular significance in view of the fact that cobalt and ruthenium solutes are shown to substitute onto Site 1 of the β-Mn crystal structure, as opposed to the more strongly magnetic Site II as for previously reported spin glass alloy systems, in which the impurity lifts magnetic frustration by removal of configurational degeneracy. Expansion appears to play a key role in β-Mn1-xRux, with the introduction of ruthenium appearing to drive the system to an intermediate state between the weak itinerant and localized moment regimes.
University of Southampton
Horn, Clare Jane
d289fa28-dbe0-4c8d-89ff-0cf728397851
2007
Horn, Clare Jane
d289fa28-dbe0-4c8d-89ff-0cf728397851
Horn, Clare Jane
(2007)
Spin fluctuations in manganese intermetallics.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Magnetic ground states and dynamics in manganese systems have been investigated for two different types of structure, the binary β-Mn1-xMx and ternary RMn4Al8 intermetallics where M represents cobalt or ruthenium and R is a rare earth element/yttrium/scandium.
For β-Mn alloys containing cobalt impunities, a static ground state of spin glass-like character has been stabilised for concentrations above 5% Co; there is an absence however of long range order in these systems, up to the highest measured concentration of 25at.% Co. The β-Mn1-xRux alloys enter a spin glass-type state for all measured concentrations (above x = 0.03), in conjunction with a higher-temperature transition to a long range antiferromagnetically ordered state for x = 0.12, co-existent with the spin glass phase. These findings are evidenced by peaks in the muon spin relaxation rate, with a characteristic stretched exponential relaxation function observed below the spin glass transition temperature. Further support is provided by susceptibility and polarized neutron measurements. Clear magnetic Bragg peaks in neutron powder diffraction data, in addition to specific heat anomalies, confirm the presence of the long-range ordered state in the ruthenium alloys. Neutron lineshapes in a number of samples of both series may also imply Non-Fermi liquid scaling.
These results are of particular significance in view of the fact that cobalt and ruthenium solutes are shown to substitute onto Site 1 of the β-Mn crystal structure, as opposed to the more strongly magnetic Site II as for previously reported spin glass alloy systems, in which the impurity lifts magnetic frustration by removal of configurational degeneracy. Expansion appears to play a key role in β-Mn1-xRux, with the introduction of ruthenium appearing to drive the system to an intermediate state between the weak itinerant and localized moment regimes.
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Published date: 2007
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Local EPrints ID: 466330
URI: http://eprints.soton.ac.uk/id/eprint/466330
PURE UUID: 98b3074c-9748-4f90-8136-21c09d7f7458
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Date deposited: 05 Jul 2022 05:10
Last modified: 16 Mar 2024 20:38
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Author:
Clare Jane Horn
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