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Abstract:
The magnetic structures and the magnetic phase transitions in the
Mn-doped orthoferrite TbFeO3 studied using neutron powder diffraction
are reported. Magnetic phase transitions are identified at T-N(Fe/Mn)
approximate to 295K where a paramagnetic-to-antiferromagnetic transition
occurs in the Fe/Mn sublattice, T-SR(Fe/Mn) approximate to 26K where a
spin-reorientation transition occurs in the Fe/Mn sublattice and T-N(R)
approximate to 2K where Tb-ordering starts to manifest. At 295 K, the
magnetic structure of the Fe/Mn sublattice in TbFe0.5Mn0.5O3 belongs to
the irreducible representation Gamma(4) (G(x)A(y)F(z) or Pb'n'm). A
mixed-domain structure of (Gamma(1) + Gamma(4)) is found at 250K which
remains stable down to the spin re-orientation transition at T-SR(Fe/Mn)
approximate to 26K. Below 26K and above 250 K, the majority phase (>80%)
is that of Gamma(4). Below 10K the high-temperature phase Gamma(4)
remains stable till 2K. At 2 K, Tb develops a magnetic moment value of
0.6(2) mu(B)/f.u. and orders long-range in F-z compatible with the
Gamma(4) representation. Our study confirms the magnetic phase
transitions reported already in a single crystal of TbFe0.5Mn0.5O3 and,
in addition, reveals the presence of mixed magnetic domains. The ratio
of these magnetic domains as a function of temperature is estimated from
Rietveld refinement of neutron diffraction data. Indications of
short-range magnetic correlations are present in the low-Q region of the
neutron diffraction patterns at T < T-SR(Fe/Mn). These results should
motivate further experimental work devoted to measure electric
polarization and magnetocapacitance of TbFe0.5Mn0.5O3. (C) 2016 AIP
Publishing LLC.
