Racetrack memory, or domain-wall memory (DWM), had contenders that included magnetoresistive random-access memory (MRAM), phase-change memory (PCRAM) and ferroelectric RAM (FeRAM) and most of these offer densities similar to flash memory.
Racetrack memory or domain-wall memory (DWM) is an experimental non-volatile memory device under development at IBM's Almaden Research Center by a team led by physicist Stuart Parkin. Other contenders included magnetoresistive random-access memory (MRAM), phase-change memory (PCRAM) and ferroelectric RAM (FeRAM). Most of these technologies offer densities similar to flash memory, in most cases worse, and their primary advantage is the lack of write-endurance limits like those in flash memory. 
