how to save a modified 3D raw file ?

Hi I am trying to read a raw file (float64, which is a deformation vector field), with 3 dimensions 304 *224 * 52. Then i want to change all the values within this file by dividing them by 10. After that I want to save the modified file again as a raw file with the same specifications. I wrote a code but I am not able to save the file. I think I might be missing something. I am a beginner in matlab so I would appreciate your help and patience. Thank you.

fid = fopen('I:\PatientData\patient1\out_2_to_1_us\deformationField_test.raw')

dvf = fread(fid);

length(div) div =(0.1)* ones(42491904,1); dvf_cm = dvf.* div;

count = fwrite(fid,dvf_cm,'float64'); fclose(fid);