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Spin reorientation behavior in YMn1-xMxO3 (M = Ti, Fe, Ga; x = 0, 0.1)

The structural and magnetic properties of polycrystalline YMn1-xMxO3 (M = Ti, Fe, Ga; x = 0, 0.1) have been studied by neutron powder diffraction and magnetic measurements to probe the effect of Mn site doping on the frustration behavior and magnetic structure of these compounds. The compounds are isostructural and crystallize with hexagonal structure in P63cm space group. We find that doping with these three ions, Ti4+ (d0), Fe3+ (d5) and Ga3+ (d10), influences both the TN and magnetic structure, unlike other Mn-site dopants reported previously. The magnetic structure of YMnO3 is described by considering a linear combination of irreducible representations Γ3 and Γ4 below TN ~ 75K and with decrease in temperature the ratio of Γ3 and Γ4 changes. The mixing ratio of these two irreducible representations remains constant on lowering of temperature in the Ga doped compounds. The magnetic structure is modified on doping with nonmagnetic ion Ti4+ (d0). It is described by the basis vectors of the irreducible representation Γ2 with moment 2.3μB at 6 K. On doping with Fe3+ (d5) the magnetic structure immediately below TN is explained by considering the Γ3 irreducible representation. On further lowering of temperature, a spin reorientation at ~ 35 K is observed. Below this temperature, the magnetic structure of YMn0.9Fe0.1O3 is explained by considering Γ3 representation with 51% mixing of Γ4. The ordered moments are found to be reduced from the expected value for a Mn3+ ion in all these compounds indicating the frustrated nature of these compounds. However, the frustration parameter, f is significantly reduced in the case of Ti doped compound with Γ2 representation.