$margin_orientation: (
  t: margin-top,
  l: margin-left,
  b: margin-bottom,
  r: margin-right
);

@each $label, $rule in $margin_orientation {
  @for $i from 0 through 9 {
    @for $j from 0 through 9 {
      .m-#{$label}-#{$i}-#{$j} {
        #{$rule}: $i + ($j / 10) + 0em;
      }
    }
  }
}