Optimizing big size structure

Hello, I am not very familiar with structure.

I have a program that request for input an obj structure with empty value in it. This is the code that returns the correct result but it is very slow. I was wondering if there were a different way to get to the same result but a lot faster?

tic
obj.FFT_h0=struct;
obj.FFT_h1=struct;
obj.FFT_h3=struct;
obj.FFT_h5=struct;
obj.FFT_h7=struct;
obj.FFT_h9=struct;

fft_buffer_size=2^14;
for i=1:fft_buffer_size
    obj.FFT_h0(i,1).timestamp=[];
    obj.FFT_h0(i,1).mag=[];
    obj.FFT_h0(i,1).phase=[];

    obj.FFT_h1(i,1).timestamp=[];
    obj.FFT_h1(i,1).mag=[];
    obj.FFT_h1(i,1).phase=[];

    obj.FFT_h3(i,1).timestamp=[];
    obj.FFT_h3(i,1).mag=[];
    obj.FFT_h3(i,1).phase=[];

    obj.FFT_h5(i,1).timestamp=[];
    obj.FFT_h5(i,1).mag=[];
    obj.FFT_h5(i,1).phase=[];

    obj.FFT_h7(i,1).timestamp=[];
    obj.FFT_h7(i,1).mag=[];
    obj.FFT_h7(i,1).phase=[];

    obj.FFT_h9(i,1).timestamp=[];
    obj.FFT_h9(i,1).mag=[];
    obj.FFT_h9(i,1).phase=[];
 end
 toc