M. Ramakrishnan

Magnetic order dynamics in optically excited multiferroic TbMnO3

We performed ultrafast time-resolved near-infrared pump, resonant soft X-ray diffraction probe measurements to investigate the coupling between the photoexcited electronic system and the spin cycloid magnetic order in multiferroic TbMnO3 at low temperatures. We observe melting of the long range antiferromagnetic order at low excitation fluences with a decay time constant of 22.3 +- 1.1 ps, which is much slower than the ~1 ps melting times previously observed in other systems. To explain the data we propose a simple model of the melting process where the pump laser pulse directly excites the electronic system, which then leads to an increase in the effective temperature of the spin system via a slower relaxation mechanism. Despite this apparent increase in the effective spin temperature, we do not observe changes in the wavevector q of the antiferromagnetic spin order that would typically correlate with an increase in temperature under equilibrium conditions. We suggest that this behavior results from the extremely low magnon group velocity that hinders a change in the spin-spiral wavevector on these time scales.

Dynamic pathway of the photoinduced phase transition of TbMnO3

We investigate the demagnetization dynamics of the cycloidal and sinusoidal phases of multiferroic TbMnO

Magnetic properties of strained multiferroic CoCr2O4: A soft x-ray study

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Multiferroic properties of uniaxially compressed orthorhombic HoMnO3 thin films

by means of time-resolved resonant soft x-ray diffraction following excitation by an optical pump. Using orthogonal linear x-ray polarizations, we suceeded in disentangling the response of the multiferroic cycloidal spin order from the sinusoidal antiferromagnetic order in the time domain. This enables us to identify the transient magnetic phase created by intense photoexcitation of the electrons and subsequent heating of the spin system on a picosecond timescale. The transient phase is shown to be a spin density wave, as in the adiabatic case, which nevertheless retains the wave vector of the cycloidal long range order. Two different pump photon energies, 1.55 eV and 3.1 eV, lead to population of the conduction band predominantly via intersite

Crystal symmetry lowering in chiral multiferroic Ba3TaFe3Si2O14 observed by x-ray magnetic scattering

d

Interplay of Fe and Tm moments through the spin-reorientation transition in TmFeO3

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Interplay between magnetic order at Mn and Tm sites alongside the structural distortion in multiferroic films ofo−TmMnO3

d

Magnetic properties of strained multiferroic

transitions or intrasite

Crystal symmetry lowering in chiral multiferroic

p

{\mathrm{Ba}}_{3}{\mathrm{TaFe}}_{3}{\mathrm{Si}}_{2}{\mathrm{O}}_{14}

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