[en] The temperature dependences of the d.c. magnetic susceptibility and Verdet constant in two zirconium based fluoride glasses have been studied. One sample has as a minor constituent dysprosium which has a large magnetic moment that dominates the material's magnetic character. The second sample, containing a small amount of europium, shows both Van Vleck paramagnetism and a Curie-Weiss behaviour. The Curie-Weiss character is believed to come from small amounts of Zr³⁺ and/or Zr²⁺ produced during the sample's manufacturing process. An upper limit is placed on the amount of magnetic zirconium in the material. (author)