Biologically encoded magnonics

Spin wave logic circuits using quantum oscillations of spins (magnons) as carriers of information have been proposed for next generation computing with reduced energy demands and the benefit of easy parallelization. Current realizations of magnonic devices have micrometer sized patterns. Here we demonstrate the feasibility of biogenic nanoparticle chains as the first step to truly nanoscale magnonics at room temperature. Our measurements on magnetosome chains (ca 12 magnetite crystals with 35 nm particle size each), combined with micromagnetic simulations, show that the topology of the magnon bands, namely anisotropy, band deformation, and band gaps are determined by local arrangement and orientation of particles, which in turn depends on the genotype of the bacteria. Our biomagnonic approach offers the exciting prospect of genetically engineering magnonic quantum states in nanoconfined geometries. By connecting mutants of magnetotactic bacteria with different arrangements of magnetite crystals, novel architectures for magnonic computing may be (self-) assembled.

The Authors have fully addressed my comments and, in general, did a great job with the improvement of the manuscript in the process of the reviewing. I recommend the manuscript for publication in its current form.
Reviewer #2 (Remarks to the Author): The revised paper appears to present the results in a more accurate form with key clarifications in appropriate places. The main accomplishment is a difficult and sensitive measurement that will interest a number of groups working on magnetic particle assemblies and may inspire future work using this technique. I believe that the manuscript is suitable for publication in Nature Communications.
Reviewer #5 (Remarks to the Author): This improved version addresses most of the referee questions. A TEM micrograph has been incorporated in the supplementary material section. It is a image of very poor quality. It is very hard to appreciate the chain kinks. It should not be difficult to obtain a higher magnification image showing for readers the details that authors state. May be that STEM-HAADF mode should be better than TEM to improve resolution. The quality and sophisticated degree of the work merit an impressive micrograph. The readers will appreciate it. I don't know what was the preparation of the sample for TEM. The authors do not describe in the Methods section the details of the preparation: use of contrast, embebed in resin? The micrographs of figures 3 and 4 are really SEM images? The method contains no information. The authors should pay attention to these issues.
Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications.
The Authors have fully addressed my comments and, in general, did a great job with the improvement of the manuscript in the process of the reviewing. I recommend the manuscript for publication in its current form.
Response: We would like to thank the referee for their positive evaluation.

Reviewer #2 (Remarks to the Author):
The revised paper appears to present the results in a more accurate form with key clarifications in appropriate places. The main accomplishment is a difficult and sensitive measurement that will interest a number of groups working on magnetic particle assemblies and may inspire future work using this technique. I believe that the manuscript is suitable for publication in Nature Communications.
Response: We would like to thank the referee for their positive evaluation.

Reviewer #5 (Remarks to the Author):
This improved version addresses most of the referee questions. A TEM micrograph has been incorporated in the supplementary material section. It is a image of very poor quality. It is very hard to appreciate the chain kinks. It should not be difficult to obtain a higher magnification image showing for readers the details that authors state. May be that STEM-HAADF mode should be better than TEM to improve resolution. The quality and sophisticated degree of the work merit an impressive micrograph. The readers will appreciate it. I don't know what was the preparation of the sample for TEM. The authors do not describe in the Methods section the details of the preparation: use of contrast, embedded in resin? The micrographs of figures 3 and 4 are really SEM images? The method contains no information.