Our laboratory is located within the Engineering Science Building of the Materials Research Laboratory and it has about 1300 ft2 of dedicated research space, which is separated into a smaller laboratory space of about 400 ft2 dedicated to sample growth and the remainder for sample characterization. Aside from our own laboratories, we frequently make use of shared user facilities at the Materials Research Laboratory as well as the Argonne National Laboratory. In the following, an overview of our own laboratory facilities and equipment will be provided.
Sample Preparation Laboratory
The sample preparation lab has a fume hood and a laminar flow clean bench, dedicated desiccated sample storage space, and two major thin film deposition tools that are currently being installed.
The first deposition tool is a sputter chamber (AJA International, ATC 2200) for con-focal deposition with thickness variation of less than ±1.5% over a 4” wafers with dc, pulsed dc and rf power to 8 magnetron sources and rf biasing of the substrate. This tool is used for deposition of metals, nitrides and oxides. 2 of the sources are mounted in an off-axis geometry for oxide and nitride growth. Samples can be grown with substrate temperatures up to 1000°C in an O2 environment.
In addition to that, we utilize an electron-beam evaporator and ion-milling chamber (AJA International, ATC 1800) with each e-beam evaporator having six different target materials and auto-indexing capability. Deposition uniformity is with thickness variations less than ±1.5% over a 4” wafers. Furthermore, there is an ion source for ion milling with ion energies up to 1200 V and a beam current above 100 mA.
Sample Characterization Laboratory
An essential tool for sample characterization is our Brillouin Light Scattering microscope (developed by THATec) with high spatial resolution (250 nm), electromagnet (GMW 5403, 2 T field with 15 mm gap) and microwave signal generator (Berkeley Nucleonics 845; up to 20 GHz) for excitation of magnetization dynamics. The scattered light is energy analyzed by a TableStable TFP-2 interferometer. The system has a fully automated scan system (based on thaTEC:OS) with long term stability for parametric studies. This system is used for studying energy flow due to spin waves, which is important for understanding the damping of magnetization dynamics and the connections between spin and charge currents.
Furthermore, a custom magneto-optic Kerr imaging system with fully automized image acquisition and vector in-plane magnetic-field capability based on a rotatable GMW 5201 electromagnet (0.35 T maximum field) is being developed and is expected to be available in late summer.
A vector network analyzer (Rhode & Schwarz ZVA67 up to 67 GHz) is used for waveguide experiments including broadband ferromagnetic resonance.
A magneto-transport measurement system with a cryogen-free 9T-2T-2T vector magnet and 50 mm diameter room temperature sample space is used for dc and rf transport characterization. Additional closed-cycle variable temperature inset with 25 mm diameter sample space is available for variable temperature measurements between 2 K and 375 K. The closed-cycle variable temperature inset is top-loading for rapid sample turn-around and has four high frequency (up to 65 GHz) connectors to the sample and additional 16 dc wire connections. This system is expected to be installed in the beginning of 2021.
Computing Equipment
A micromagnetic simulation code (mumax) is used on a dedicated computer system with a Nvidia GeForce RTX 2080 ti GPU for modeling static and dynamic magnetization structures. Furthermore, we also use the Object Oriented MicroMagnetic Framework (OOMMF) as an alternative tool for micromagnetic simulations.