Information recording and reproducing device

An information recording and reproducing device comprising:

• a recording layer made of a first layer containing a second compound including an oxide including a first positive ion element made of a transition metal element and serving as a first positive ion having a d orbital incompletely filled with electrons;
• and
• a driving unit configured to generate a phase change in the recording layer and to record information by one of application of a voltage to the recording layer and application of a current to the recording layer,
• a coordination number of another of the first positive ion element at a position of a second coordination of the first positive ion element being 80% or more and less than 100% of the coordination number when the second compound being assumed to be a perfect crystal.

An information recording and reproducing device comprising:

• a recording layer including a first layer containing a third compound including:
• a third positive ion made of a transition metal element, having a d orbital incompletely filled with electrons and having a first valence;
• and
• a fourth positive ion made of an element being same type as the third positive ion and having a second valence different from the first valence;
• and
• a driving unit configured to generate a phase change in the recording layer and to record information by one of application of a voltage to the recording layer and application of a current to the recording layer,
• a coordination number of the third positive ion at a position of a second coordination of the fourth positive ion being 80% or more and less than 100% of the coordination number when the third compound being assumed to be a perfect crystal.