Academic Events

Physics Colloquium: L10 -phase FePd thin films with low damping and high thermal stability for semiconductor-compatible high performance memory

Name: Physics Colloquium: L10 -phase FePd thin films with low damping and high thermal stability for semiconductor-compatible high performance memory
Start: 2023-02-28T15:15:00-05:00
End: 2023-02-28T16:30:00-05:00
Location: Regents Hall, Room 109

Dr. Daniel Gopman, NIST

Abstract: The demand for smaller, faster and ultra-low power compute technologies continues to grow with the propagation of smart sensors, mobile technologies and the broader Internet of Things. The increasing density of complementary memory technologies has caused significant increases in static and dynamic power consumption in electronic devices. Due to their virtually zero static power consumption, magnetic memory and logic devices hold significant promise for advanced microelectronics systems. Magnetic random access memory (MRAM), based on the two-terminal, electrically writable magnetic tunnel junction (MTJ), is being applied today at low densities as AI chip accelerators as well as persistent memory units in automotive chips. To reach ultrahigh densities, MRAM is following a similar trend seen in magnetic storage with a transition to materials with a strong perpendicular magnetic anisotropy (PMA), an enabler for data retention in the smallest magnetic feature sizes. Although present-day MTJs exhibit PMA due to a strong interfacial PMA at the interfaces of a Co-Fe-B amorphous alloy within heavy metal/CoFeB/MgO trilayer, ultrahigh density MRAM with sub-20 nm lateral sizes demands materials possessing bulk magnetocrystalline anisotropy. L10-phase intermetallic structures fall into this category, including Mn-, Co- and Fe-based alloys, presenting a range of alternatives with requisite PMA energy density at the MJ/m3 range. Amongst these materials, L10 FePd shows strong promise to realize high-speed and high-density MRAM, due to the large PMA, low Gilbert damping and integrability into complex synthetic ferrimagnetic free layer structures for low-write energy switching.

I will present results on L10 phase FePd thin films with low damping and high thermal stability for high performance memory. The FePd films are grown on noble-metal buffer layers (including Ru, Ir, Pt and Rh) deposited on single-crystalline MgO(001) substrates using direct current magnetron sputtering in a custom 13-target ultrahigh vacuum facility (base pressure < 7 x 10-8 Pa). Temperature-dependent measurements of the perpendicular magnetic anisotropy (PMA) energy and Gilbert show that films with a strong degree of L10 ordering suffer only marginal reductions in the PMA field at elevated (150 °C) temperature, a prerequisite for non-volatile RAMs for automotive solutions.

I will also highlight our progress on advancing CMOS semiconductor-compatible processing of L10 phase FePd thin films and FePd|Ir|FePd synthetic antiferromagnets grown directly on Si//SiO2 substrates with appropriate buffer layers and thermal annealing. Fully-epitaxial growth from each crystallite of a sputtered, polycrystalline MgO seed layer induces the (001) texture of L10-FePd, and extends through the Ir SAF spacer.

Support for this work comes in part from DARPA “Foundations required for novel compute” and from the National Institute of Standards and Technology.