having legend title and enlarging legend marker size at the same time

Initially I had a legend as like this

As you can see, the size of the legend marker is much smaller than the size of the scatter marker. However, the legend has a title. I used below code for this:

lgd=legend('25','50','75','100','Location','northwest','FontSize',30);  
lgd.Title.String = 'Recoating Velocity (%)';
lgd.Title.FontSize = 30;

Then, in order to increase the marker size in the legend, I used the icons as below:

[lgd,icons,plots,legend_text] = legend('25','50','75','100', 'Location', 'Northwest')
for k = 5:8
    icons(k).Children.MarkerSize = 20;
end
lgd.Title.String = 'Recoating Velocity (%)';
lgd.Title.FontSize = 30;

And the result looks like this:

Although the marker size increased, but the legend title is not applied. Why is that? How to fix it?