On July 15, 2022, the team of Professor Liu Shengzhong of Shaanxi Normal University, in collaboration with professor Jin Kexin and associate professor Wang Shuohu of Northwestern Polytechnical University, published a new study on Matter titled “First Observation of Magnon Transport in Organic-Inorganic Hybrid Perovskite”.
By constructing the non-local structure of Pt/MAPbBr3/YIG, relying on the spin Seebeck effect and the reverse spin Hall effect, the research group studied the magnetic oscillator transport behavior of organic-inorganic hybrid perovskite films, and the study found that perovskite films have long magnetic oscillator diffusion performance, which fully demonstrates the advantages of such semiconductors as spintron materials. The corresponding authors of the paper are Liu Shengzhong, Jin Kexin, Wang Shuohu; The first author is Ren Lixia.
Organic-inorganic hybrid perovskite (abbreviated as OICHP) prototyped by MAPbBr3 has become a new generation of solution-processed semiconductors, due to its high carrier mobility, long carrier life, strong photoluminescence and other excellent photoelectric properties, OIHP has attracted widespread attention and in-depth research in the field of photovoltaics. As the research progressed, the Rashba effect and the magnetic field effect were gradually observed in the OIHP, and the analysis learned that these strong spin orbit couplings (SOC) caused by heavy elements such as lead and halogen were analyzed. And the giant magnetoresistance effect observed in the MAPbBr3 thin film in recent years fully reveals the electron spin performance of such materials, and its electron spin transport parameters can be comparable to traditional semiconductors, so people pay attention to the spin properties of OIHP and its prospects in spin electronic devices. However, due to the structural design, there is a lack of magnetron injection studies in the study of related OICHP materials, resulting in a lack of understanding of their magnetic oscillator properties.
As an important research area of spintronics, magnetronology is expected to reduce the energy dissipation caused by the movement of free charges and replace electrons as information carriers with spin waves (magnetic oscillators). Therefore, magnetronology plays an important role in telecommunications systems and radar applications. Usually the spin angular momentum stream is called spin current (JS). In solids, there are two types of carriers for non-equilibrium spin flows, namely conductive electrons and magnetic oscillators. To differentiate, we refer to the spin stream carried by the magnetic oscillator as the “magnetic oscillator flow”. The magnetic oscillator stream can be generated by the Spin Seebeck effect (SSE for short). Converting a magnetic oscillator stream into an Electric charge current and regulating this behavior, and vice versa, are core elements of magnetron research. The detailed process can be described as follows: for heterogeneous structures composed of ferromagnetic materials (FM) and non-magnetic materials (NM), when the heterogeneous interface is affected by temperature gradient (▽T), the heat-driven magnetic oscillator stream will be injected into the NM from the adjacent FM. This means that ▽T causes a finite gradient distribution of the magnetic oscillator stream, i.e. causes the magnetic oscillator to diffuse the transmission. When the magnetic oscillator stream is transmitted to an NM with a strong SOC, the Inverse spin Hall effect (ISSE for short) converts it into an electrical signal. Therefore, ISHE is a powerful tool for detecting spin flow, and it is also commonly used in the study of magnetic oscillator transport.
It is known that efficient magnetic oscillator injection is a prerequisite for the design and development of many magnetic oscillator devices, and it is also one of the key contents of magnetic oscillator research. In this work, we used an excellent magnetic material, yttrium iron garnet (Y3Fe5O12, abbreviated as YIG), as a magnetron source with extremely low magnetic damping; Design Pt/MAPbBr3/YIG non-local structure, and inject magnetic oscillator streams into the OICHP film through SSE; Combined with the ISHE system, it was studied and revealed for the first time the transport behavior of magnetic oscillators in OICHP films.
As shown in Figure 1, the YIG film is first epitaxially grown on a (111) oriented gadolinium gallium garnet (Gd3Ga5O12, abbreviated as GGG) substrate by spin coating method, using a laser heating method to produce a local ▽T. This enables the injection of a magneton stream from the YIG layer into the MAPbBr3 film. Since MAPbBr3 exhibits very high resistivity in the dark, we can determine that what is transmitted in the MAPbBr3 layer is a magnetic oscillator stream (i.e., a diffusion that does not contain spin electrons), which subsequently diffuses further to the Pt layer. In the Pt layer, due to its strong SOC, the spin current can be converted into a voltage (VISHE) is detected, as shown in Figure 2. It is calculated that the magnetic oscillator diffusion length of THE MAPbBr3 film at room temperature can reach 55.6 nm.
Figure 1: Schematic diagram of the spin Seebeck effect and the reverse spin Hall effect.
Figure 2: Magnetic oscillator transport in MAPbBr3 thin film is characterized.
A series of OIHP films were prepared by changing the composition: FAPbBr3, MAPbI3, and then the magnetic oscillator transport behavior of the sample composed of these perovskite films was characterized, as shown in Figure 3. It was observed that the magnetic oscillator diffusion of FAPbBr3 thin films was longer compared to MAPbBr3; MAPbI3 films are shorter. It can be seen that unlike spintron transport, the organic and inorganic components of OIHP films play an important role in the transport of magnetic oscillators, which are closely related to SOC and ultrafine interaction (HFI), respectively.
Figure 3: Magnetic oscillator transport characterization of FAPbBr3, MAPbI3 and other thin films.
As shown in Figure 4, it is found that the magnetic oscillator diffusion length of OIHP is better than some of the currently known insulating intermediate layer materials, such as NiO, GGG, SrTiO3, CoO, etc., and even better than some metal materials, such as Au. In addition, although the magnetic oscillator diffusion of OHIP is not as good as that of metal Cu, the metalliness of Cu will short-circuit the magnetic oscillator signal, limiting its application in magnetic oscillator devices. Therefore, there is reason to believe that OICHP has the potential to become a dominant material in the field of magnetron research. In addition, we also found that the magnetic oscillator diffusion of MAPbBr3 is longer than its electron spin diffusion, which is caused by the inelastic scattering and spin coherence of the electrons being lost as the electrons move.
Figure 4: Comparison of magnetic oscillator transport performance of a series of intermediate layer materials.
At the end of the article, we also proved that OICHP thin films as magneton transport layers apply not only to ferromagnetic insulating materials, but also to ferromagnetic metal materials (NiFe), as shown in Figure 5.
Figure 5: SSE characterization with NiFe as the magneton source.
(Source: Science Network)
Related paper information:https://doi.org/10.1016/j.matt.2022.06.053