1,359 research outputs found
Magnetic and the magnetocaloric properties of Ce1-xRxFe2 and Ce(Fe1-xMx)2 compounds
We have studied selected rare earth doped and transition metal doped CeFe2
compounds by examining their structural, magnetic and magneto-thermal
properties. With substitution of Ce by 5 and 10% Gd and 10% Ho, the Curie
temperature can be tuned to the range of 267-318 K. Localization of Ce 4f
electronic state with rare earth substitutions is attributed for the
enhancement of Curie temperature. On the other hand, with Ga and Al
substitution at the Fe site, system undergoes paramagnetic to ferromagnetic
transition and then to an antiferromagnetic phase on cooling. The
magnetocaloric effect across the transitions has been studied from both
magnetization isotherms and heat capacity data. It is shown that by choosing
the appropriate dopant and its concentration, the magnetocaloric effect around
room temperature can be tuned.Comment: 13 pages, 6 figures, 2 table
Magnetism in Gallium doped CeFe_2: The martensitic scenario
Ce(Fe_{1-x}Ga_x)_2 compounds with x = 0, 0.01, 0.025 and 0.05 have been
investigated to unravel the effect of Ga on the magnetic state of CeFe_2. For
the first time, we find that the dynamic antiferromagnetic phase present in
CeFe_2 gets stabilized with Ga substitution. The hysteresis loops show that
while the compounds with x = 0 and 0.01 show normal behavior, the other two
show multiple magnetization steps across the antiferromagnetic-ferromagnetic
transition region. The virgin curve is found to lie outside the envelope curve
in these two compounds, similar to the observations made in Ru and Re
substituted CeFe_2 compounds. Temperature, sweep rate and time dependences of
the magnetization show that the compounds with x >=0.025 possess glassy
behavior at low temperatures. Various results obtained reveal that these two
compounds belong to the martensite family.Comment: 23 pages, 12 Figure
Observation of re-entrant spin glass behavior in (Ce1-xErx)Fe2 compounds
Clear experimental evidence of re-entrant spin glass state has been revealed
in Er doped CeFe2 compounds. The zero field cooled - field cooled bifurcation
in dc magnetization, frequency dependence of freezing temperature, relaxation
in zero field cooled magnetization and presence of large remanence confirm the
spin glass state in these compounds. Frequency dependence is found to follow
the critical slowing down mechanism. The random substitution of Er and the
change in the valence state of Ce along with an enhancement of the
ferromagnetic component in the Fe sublattice seem to be responsible for the
spin glass state. Using detailed experimental protocols, we also prove that the
low temperature state in these compounds is not a magnetic glass. The absence
of exchange bias gives an indication that there is no coexistence of
ferromagnetism and spin glass state in these compounds. The RSG state is found
to be associated with the randomly magnetized clusters instead of atomic level
randomness.Comment: 19 pages, 9 figure
Stabilization of antiferromagnetism in CeFe2 alloys: Effects of chemical and hydrostatic pressure
Effects of Al, Mn and Sb dopings in CeFe2 and effect of applied pressure have
been investigated. Al doping gives rise to the FM-AFM transition and a
reduction in the magnetic moment and TC values, clearly indicating the growth
of the AFM component. Mn and Sb dopings only cause a reduction in TC value. It
is found that in general external pressure enhances the antiferromagnetism in
both the pure and the doped alloys. Enhancement of the Ce 4f- Fe 3d
hybridization as a result of dopings and with the external pressure may be the
reason for the stabilization of antiferromagnetism in these alloys.Comment: 14 pages, 7 figure
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