Canted antiferromagnetism and magnetoelastic coupling in metallic Ho0.1Ca0.9MnO3

Ho0.1Ca0.9MnO3 is a canted antiferromagnet with the magnetic space group Pn'ma'. The magnetic structure is a superposition C(x)F(y)A(z) of the three types of order allowed in Pn'ma'. In the Carich corner of the system Ho1-xCaxMnO3 the title compound has a strong magnetoelastic distortion Delta V-MAG/V = 1.2 x 10(-3), the highest metallic conductivity and a ferromagnetic component F-y close to the maximum in the series. Among the areas ab, bc, ca calculated from the lattice constants only ca shows a strong magnetoelastic effect below T-N = 106 K. The x-, y-, z-spin components depend differently on the temperature. This gives rise to spin rotation which is particularly strong close to T-N. MnO6 octahedra have short bond lengths with a temperature independent average [MnO] = 1.91 Angstrom. They are practically regular at room temperature and show a Jahn-Teller distortion of 3.5% in the magnetically ordered state. Above T-N we find small polaron conductivity. The presence of the Jahn-Teller distortion due to the only small abundance (10%) of Mn3+ in the t(2g)(3)e(g) configuration is attributed to delocalised e(g) electrons. In the magnetically ordered state the averaged magnetic moment of Mn is reduced appreciably from the paramagnetic value due to spin disorder.