Faster, farther, stronger: spin transfer torque driven high order propagating spin waves in nano-contact magnetic tunnel junctions

TL;DR

This paper demonstrates nano-contact based spin wave generation in magnetic tunnel junctions, revealing higher-order spin waves with shorter wavelengths that can significantly enhance magnonic device performance at higher frequencies.

Contribution

It introduces the generation of higher-order propagating spin waves in magnetic tunnel junctions, enabling higher frequencies and improved transmission for magnonic devices.

Findings

Observation of second and third order spin waves with wavelengths of 120 and 74 nm

Demonstration of spin waves with wavelengths smaller than the nano-contact diameter

Potential for higher frequency operation and increased transmission rates in magnonic devices

Abstract

Short wave-length exchange-dominated propagating spin waves will enable magnonic devices to operate at higher frequencies and higher data transmission rates.1 While GMR based magnetic nano-contacts are highly efficient injectors of propagating spin waves2,3, the generated wave lengths are 2.6 times the nano-contact diameter4, and the electrical signal strength remains much too weak for practical applications. Here we demonstrate nano-contact based spin wave generation in magnetic tunnel junction stacks, and observe large discrete frequency steps consistent with the hitherto ignored possibility of second and third order propagating spin waves with wave lengths of 120 and 74 nm, i.e. much smaller than the 150 nm nano-contact. These higher-order propagating spin waves will not only enable magnonic devices to operate at much higher frequencies, but also greatly increase their transmission rates and spin wave propagating lengths, both proportional to the much higher group velocity.