Polaronic Transport Induced by Competing Interfacial Magnetic Order in aLa0.7Ca0.3MnO3/BiFe

Abstract

Using ultrafast optical spectroscopy, we show that polaronic behavior associated with interfacial antiferromagnetic order is likely the origin of tunable magnetotransport upon switching the ferroelectric polarity in a La 0.7 Ca 0.3 MnO 3 =BiFeO 3 (LCMO/BFO) heterostructure. This is revealed through the difference in dynamic spectral weight transfer between LCMO and LCMO/BFO at low temperatures, which indicates that transport in LCMO/BFO is polaronic in nature. This polaronic feature in LCMO/BFO decreases in relatively high magnetic fields due to the increased spin alignment, while no discernible change is found in the LCMO film at low temperatures. These results thus shed new light on the intrinsic mechanisms governing magnetoelectric coupling in this heterostructure, potentially offering a new route to enhancing multiferroic functionality. The quest to achieve strong magnetoelectric coupling has driven the surge in research on multiferroic materials over the past decade. However, this has been quite difficult to accomplish using bulk materials, motivating researchers to explore other approaches, most notably the use of transition metal oxide heterostructures [1][2][3]. In these novel systems, different degrees of freedom (DOFs) (e.g., charge, spin, and orbital) are coupled at a single interface between two different oxide layers to form a new state that displays properties dramatically different from those of the individual layers [4][5][6][7][8]. Particular attention has been given to the coupling between ferromagnetic (FM), antiferromagnetic (AFM), and ferroelectric (FE) orders, as this could reveal new routes to realizing strong magnetoelectric coupling [1][2][3][9][10][11].Heterostructures consisting of manganite and multiferroic layers are particularly promising in this regard. The most extensively studied combination [2,3,9,10,12] consists of the colossal magnetoresistive manganite La 0.7 Sr 0.3 MnO 3 (LSMO) [or the similar compound La 0.7 Ca 0.3 MnO 3 (LCMO)], which is ferromagnetic below a critical temperature T c , and the canonical multiferroic BiFeO 3 (BFO), which has coexisting coupled AFM and FE phases in which the magnetization can be switched by an applied electric (E) field [13]. The combination of these materials thus has great potential for exhibiting novel phenomena by coupling different FM, AFM, and FE phases across the interface. Indeed, a new interfacial state between LSMO and BFO has been discovered experimentally and discussed theoretically [2,[14][15][16]. This state displays an exchange-bias field and magnetotransport that can be tuned by switching the FE polarization, increasing the potential for device control through interfacial coupling. However, a complete picture of the interplay between FM and AFM orders in this heterostructure has yet to be reached.Current understanding of the exchange-bias field, which arises from the interaction between FM and G-type AFM [AFMðGÞ] orders at the interface, is based on spin canting or pinning in BFO, with the assumption of negligible canting in ...

Evolution of Hot Polaron States with a Nanosecond Lifetime in a Manganite Perovskite

“…[27,[45][46][47] A quantitative evaluation of heating of the PCMO film and heat diffusion into the MgO substrate (Section 16.2, Supporting Information) reveals a heat decay constant and a heat induced optical density change, which are in quite good agreement with τ slow and A slow at room temperature. This and the absence of a photovoltaic effect due to bulk photodiffusion gives strong evidence, that heat diffusion governs the nanosecond process above T CO .…”

Real-time decay of a highly excited charge carrier in the one-dimensional Holstein model

“…Figure 3(b) shows the convergence of the time-dependent phonon energy E ph (t) at λ = 0.5 with respect to the parameters N h and M of the basis generator in Eq. (16). With increasing N h , the data converge fast.…”

“…However, when the electron-phonon coupling is further increased, a larger phonon cutoff is required, and consequently the full Hilbert space exceeds the available computational resources while the structure of the LFS can be tuned by increasing the parameter M in Eq. (16). Figure 3(b) shows the convergence of the time-dependent phonon energy E ph (t) at λ = 0.5 with respect to the parameters N h and M of the basis generator in Eq.…”

“…This property can be captured by tuning the parameter M [102] since the maximal number of phonons on the site of the electron is N h × M. Note that the generator of states in Eq. (16) does not represent the only possibility to efficiently truncate the phonon number; for alternative methods of creating distinct phonon configurations see, e.g., Refs. [111,112].…”

Correlating quasiparticle excitations with quantum femtosecond magnetism in photoexcited nonequilibrium states of insulating antiferromagnetic manganites

“…In this way, femtosecond (fs) laser pulses can be used to create a quasi-instantaneous electronic "initial condition" for non-adiabatic time evolution prior to lattice thermalization [4][5][6][7][8]. The physical properties of complex materials such as the manganites [9] are governed by collective order and fluctuations of coupled degrees of freedom [10][11][12][13][14]. This results in elementary excitations and order parameters with coupled charge, orbital, spin, and lattice components, which makes it difficult to underpin their microscopic composition [8,[15][16][17][18][19].…”