**2. Experimental**

## *2.1. Materials*

Samples of scrap magnets were obtained from end-of-life computer hard drives from the IT Department of Montana Tech. Ammonium hydroxide (NH4OH) dissolved in water at 28–30% concentration was obtained from VWR International LLC. Sulfuric acid (98% H2SO4) from Pharmco Products Inc. and ammonium bifluoride (98.8% NH4F·HF) manufactured by J.T. Baker were the other reagents used in the work.

#### *2.2. Sample Preparation*
