Structural dynamics in FeRh during a laser-induced metamagnetic phase transition

Quirin, F.; Vattilana, Michael; Shymanovich, U.; El-Kamhawy, Abd-Elmoniem; Tarasevitch, A.; Hohlfeld, J.; Linde, D. von der; Sokolowski‐Tinten, K.

doi:10.1103/physrevb.85.020103

Cited by 35 publications

(23 citation statements)

References 23 publications

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“…Note that any significant contribution of a single laser pulse to driving the phase transition is unlikely because the pump pulse fluence (about 0.1 mJ/cm 2 ) is ten times smaller than the critical fluence found in previous pump-probe works on comparable samples. 37 From the DC conductivity of FeRh (3.3·10 5 S/m, Ref. 38), we deduce a coupling function comparable to that of the 12 nm thick CoFeB/Pt reference sample, whereas is twice as large as for the 22 nm thick reference sample (see Eq.…”

Section: Ferhmentioning

confidence: 81%

Terahertz Spin Currents and Inverse Spin Hall Effect in Thin-Film Heterostructures Containing Complex Magnetic Compounds

Seifert

Martens

Günther

et al. 2017

SPIN

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Terahertz emission spectroscopy (TES) of ultrathin multilayers of magnetic and heavy metals has recently attracted much interest. This method not only provides fundamental insights into photoinduced spin transport and spin-orbit interaction at highest frequencies, but has also paved the way for applications such as e±cient and ultrabroadband emitters of terahertz (THz) electromagnetic radiation. So far, predominantly standard ferromagnetic materials have been exploited. Here, by introducing a suitable¯gure of merit, we systematically compare the strength of THz emission from X/Pt bilayers with X being a complex ferro-, ferri-and antiferromagnetic metal, that is, dysprosium cobalt (DyCo 5 ), gadolinium iron (Gd 24 Fe 76 ), magnetite (Fe 3 O 4 ) and iron rhodium (FeRh). We¯nd that the performance in terms of spin-current generation not only depends on the spin polarization of the magnet's conduction electrons, but also on the speci¯c interface conditions, thereby suggesting TES to be a highly interface-sensitive technique. In general, our results are relevant for all applications that rely on the optical generation of ultrafast spin currents in spintronic metallic multilayers.

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Section: Ferhmentioning

confidence: 81%

Terahertz Spin Currents and Inverse Spin Hall Effect in Thin-Film Heterostructures Containing Complex Magnetic Compounds

Seifert

Martens

Günther

et al. 2017

SPIN

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“…15,16 How the lattice and magnetic (electronic/spin) degrees of freedom give rise to these quantities, and what critical role they play in the phase transition remains an contemporary question that has gained recent impetus in light of a new class of experiments able to directly probe these degrees of freedom with picosecond temporal resolution. [17][18][19][20][21][22] Early local (local density approximation) density functional theory (DFT) work by Moruzzi and Marcus 9 demonstrated a number of AF structures, the ground state being referred to as the AFMII phase [see Fig. 1(a)].…”

Section: Introductionmentioning

confidence: 99%

Landau-Heisenberg Hamiltonian model for FeRh

Derlet

2012

Phys. Rev. B

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An empirical model is developed for the FeRh system with the view of gaining further insight into the first-order antiferromagnetic-ferromagnetic (AFM-FM) and volume phase transition known to occur at 370 K. A volume-per-atom dependent minimal nearest neighbor Landau-Heisenberg Hamiltonian is employed in which longitudinal and transverse moment fluctuations are considered for both the Fe and Rh atoms. As a function of volume-per-atom, the corresponding onsite Landau function coefficients and the nearest-neighbor exchange parameters are fitted directly to a wide range of existing colinear and noncolinear density functional theory calculations. Using a developed Monte Carlo strategy the thermal properties of the AFM and FM phases are investigated, as well as the phase transition. It is found that the model is able to describe well the thermal expansion, heat capacities and the associated entropy increase that accompanies the magnetic/volume phase transition. The model suggests an equally important role for the magnetic and volume fluctuations in driving the phase transition.

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“…[17,18] Ultrafast electron diffraction (UED) or ultrafast x-ray diffraction (UXRD) experiments that directly observe the transient lattice strain induced by ultrafast demagnetization have been discussed only sporadically. [4,5,[19][20][21] Several ultrafast diffraction studies on the transition metals Ni and Fe [22][23][24] discuss the strain waves excited by electron and phonon stresses σ e and σ ph , and theory predicts relevant electron-phonon (e-ph) coupling constants [25] even with mode-specificity.[26] Very recently granular FePt films were studied by UED. The rapid out-of-plane lattice contraction could be convincingly ascribed to changes of the free energy of the spin system.[5] The macroscopic Grüneisen coefficients (Gc) Γ e,ph describe the efficiency for generating stress σ e,ph = Γ e,ph ρ Q e,ph by a heat energy density ρ Q e,ph .[27] If Γ e = Γ ph , ultrafast diffraction allows inferring the time-dependent σ(t) from the observed transient strain ε(t).…”

mentioning

confidence: 99%

Ultrafast negative thermal expansion driven by spin disorder

et al. 2019

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We measure the transient strain profile in a nanoscale multilayer system composed of Yttrium, Holmium and Niobium after laser excitation using ultrafast X-ray diffraction. The strain propagation through each layer is determined by transient changes of the material-specific Bragg angles. We experimentally derive the exponentially decreasing stress profile driving the strain wave and show that it closely matches the optical penetration depth. Below the Neel temperature of Ho, the optical excitation triggers negative thermal expansion, which is induced by a quasi-instantaneous contractive stress, and a second contractive stress contribution rising on a 12 ps timescale. These two timescales have recently been measured for the spin-disordering in Ho [Rettig et al, PRL 116, 257202 (2016)]. As a consequence we observe an unconventional bipolar strain pulse with an inverted sign travelling through the heterostructure.In most of the research on ultrafast magnetism the lattice was only considered as an angular momentum sink.[1-3] Ultrafast effects on the lattice induced by demagnetization have been discussed surprisingly rarely.[4-7] Time-resolved magneto-optical Kerr measurements and optical picosecond ultrasonics are the workhorse for many researchers. [1,2,[8][9][10][11][12] Specialized techniques allow for assigning timescales to specific electronic processes and orbitals or bands. [3,[13][14][15][16]] This is particularly relevant in the magnetic rare earths, where the exchange interaction between the localized 4f spin and orbital magnetic moments is mediated by the itinerant 5d6s conduction electrons via the RKKY interaction. [17,18] Ultrafast electron diffraction (UED) or ultrafast x-ray diffraction (UXRD) experiments that directly observe the transient lattice strain induced by ultrafast demagnetization have been discussed only sporadically. [4,5,[19][20][21] Several ultrafast diffraction studies on the transition metals Ni and Fe [22][23][24] discuss the strain waves excited by electron and phonon stresses σ e and σ ph , and theory predicts relevant electron-phonon (e-ph) coupling constants [25] even with mode-specificity.[26] Very recently granular FePt films were studied by UED. The rapid out-of-plane lattice contraction could be convincingly ascribed to changes of the free energy of the spin system.[5] The macroscopic Grüneisen coefficients (Gc) Γ e,ph describe the efficiency for generating stress σ e,ph = Γ e,ph ρ Q e,ph by a heat energy density ρ Q e,ph .[27] If Γ e = Γ ph , ultrafast diffraction allows inferring the time-dependent σ(t) from the observed transient strain ε(t).[22, 23, 28] Hooke's law relates ε linearly to σ and hence to the energy densities ρ Q e,ph deposited in each subsystem. This concept was extended to stress resulting from spin-excitations in Ni and Fe [29,30] but the experimental verification remained ambiguous. [22][23][24] Thermodynamic analysis affirms that the Gcs generally measure how entropy S depends on strain ε.[31] The phenomenon of negative thermal expansion (NTE) generally oc...

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Structural dynamics in FeRh during a laser-induced metamagnetic phase transition

Cited by 35 publications

References 23 publications

Terahertz Spin Currents and Inverse Spin Hall Effect in Thin-Film Heterostructures Containing Complex Magnetic Compounds

Terahertz Spin Currents and Inverse Spin Hall Effect in Thin-Film Heterostructures Containing Complex Magnetic Compounds

Landau-Heisenberg Hamiltonian model for FeRh

Ultrafast negative thermal expansion driven by spin disorder

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