Role of magnetic chirality in polarization flip upon commensurate-incommensurate magnetic phase transition in YMn${}_2$O${}_5$

Abstract

We have performed simultaneous measurements of magnetic chirality by using polarized neutrons and electric polarization along the b-axis of single crystals of YMn${}^{4+}$(Mn${}_{1-x}$Ga${}_x$)${}^{3+}$O${}_5$ with $x=0.047$ and 0.12, in which nonmagnetic Ga-ions dilute Mn${}^{3+}$ spins. The $x=0.047$ sample exhibits high-temperature incommensurate (HT-ICM), commensurate (CM), and low-temperature incommensurate (LT-ICM) magnetic phases in order of decreasing temperature, whereas the $x=0.12$ sample exhibits only HT-ICM and LT-ICM phases. Here, the CM and LT-ICM phases are ferroelectric and weak-ferroelectric, respectively. Measurements conducted under zero field heating after various field-cooling conditions evidence that the microscopic mechanisms of the spin-driven ferroelectricity in the CM and LT-ICM phases are different: the magnetic chirality of Mn${}^{4+}$ cycloidal spins plays a dominant role in the LT-ICM phase, whereas the magnetic exchange striction by the Mn${}^{4+}$-Mn${}^{3+}$ chain plays a dominant role in the CM phase. The polarization of YMn${}_2$O${}_5$ flips upon CM to LT-ICM phase transition because the ferroelectricity driven by the magnetic chirality and the exchange striction provides opposite directions of polarization.

5 pages, 5 figures

References in corpus (5)

• Spin current and magneto-electric effect in non-collinear magnets
• Role of the Dzyaloshinskii-Moriya interaction in multiferroic perovskites
• Coupled magnetic and ferroelectric domains in multiferroic Ni3V2O8
• Complex Spin Structures and Origin of the Magneto-Electric Coupling in YMn2O5
• The incommensurate magnetic structure of YMn2O5: a stringent test of the multiferroic mechanism

Cited by in corpus (3)

• Reduced crystal symmetry as origin of the ferroelectric polarization within the incommensurate magnetic phase of TbMn2O5
• Electronic charge transfer driven by spin cycloidal structure
• Direct control of magnetic chirality in NdMn2O5 by external electric field