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Department of Physics and Astronomy

NovoMag

Cobalt nitrides

The cobalt nitride system has been studied in detail using adaptive genetic algorithm and first-principles calculations [1].

Materials synthesis under far-from equilibrium conditions has become an important route for materials design and discovery which can drive systems toward metastable configurations which could possess otherwise unattainable functionality.  Through crystal structure searches using adaptive genetic algorithm, we have explored metastable structures of binary cobalt nitrides for possible candidates for rare-earth free permanent magnets. New structures of ConN (n = 3…8) are found to have lower energies than those previously discovered by experiments. Some structures exhibit large magnetic anisotropy energy, reaching as high as 200 μeV per Co atom (or 2.45 MJ/m3) based on first-principles density functional calculation. Our theoretical predictions provide useful insights into a promising system for discovery of new rare-earth free magnets and useful guideline for our experimental partner at University of Nebraska-Lincoln to work on this system.

In the following table, selected structures are listed together with their magnetic properties. All the listed MAE values are either uniaxial (positive) or easy plane anisotropy (negative). Each structure is provided in the format of .cif  by clicking the structure ID.

[1] X Zhao, L Ke, CZ Wang, and KM Ho, Metastable cobalt nitride structures with high magnetic anisotropy for rare-earth free magnets. Physical Chemistry Chemical Physics 18 (46), 31680-31690 (2016).

Structure ID

Energy (eV/atom)

Space Group

Magnetic properties

CoN-1

-7.58865

F -4 3 m

M(Co) ~ 0 μB/atom

CoN-2

-7.52912

P 63 m c

M(Co) ~ 0 μB/atom

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Co2N-1

-7.40668

P 21/n 21/n 2/m

M(Co) = 0.093 μB/atom

Co2N-2

-7.3613

C 2/m 2/c 21/m

M(Co) = 0.512 μB/atom

Co2N-3

-7.3544

P 1

M(Co) = 0.013 μB/atom

Co2N-4

-7.34283

P 1

M(Co) = 0.230 μB/atom

Co2N-5

-7.32207

P m n 21

M(Co) = 0.502 μB/atom

Co2N-6

-7.3129

P 21/m 2/m 2/a

M(Co) = 0.758 μB/atom

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Co3N-1

-7.29189

R -3 2/c (hexagonal axes)

M(Co) = 0.899 μB/atom

MAE = 1.39 MJ/m3

Co3N-2

-7.29094

P 63 2 2

M(Co) = 0.974 μB/atom

MAE = 0.22 MJ/m3

Co3N-3

-7.25681

C 2/m 2/c 21/m

M(Co) = 0.770 μB/atom

Co3N-4

-7.24644

C 2/m 2/c 21/m

M(Co) = 1.354 μB/atom

MAE = 1.73 MJ/m3

Co3N-5

-7.2464

C 2/m 2/m 2/m

M(Co) = 1.376 μB/atom

MAE = -1.09 MJ/m3

Co3N-6

-7.23456

C 1 m 1

M(Co) = 0.778 μB/atom

Co3N-7

-7.22149

C 2/m 2/c 21/m

M(Co) = 0.938 μB/atom

Co3N-8

-7.22131

I 2/m 2/m 2/m

M(Co) = 1.059 μB/atom

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Co4N-1

-7.22417

P 1 21/c 1

M(Co) = 1.160 μB/atom

Co4N-2

-7.22126

C 1 2 1

M(Co) = 1.124 μB/atom

Co4N-3

-7.21482

P 21 21 2

M(Co) = 1.196 μB/atom

MAE = -0.61 MJ/m3

Co4N-4

-7.21391

P 4/m -3 2/m

M(Co) = 1.587 μB/atom

Co4N-5

-7.21218

P 2/m 2/n 21/a

M(Co) = 1.204 μB/atom

MAE = 1.35 MJ/m3

Co4N-6

-7.21153

I 4/m 2/m 2/m

M(Co) = 1.582 μB/atom

MAE = 1.88 MJ/m3

Co4N-7

-7.21009

C 2/m 2/c 21/m

M(Co) = 0.989 μB/atom

Co4N-8

-7.2038

I 4/m 2/m 2/m

M(Co) = 1.530 μB/atom

MAE = 2.45 MJ/m3

Co4N-9

-7.20212

P 21/m 2/m 2/a

M(Co) = 1.321 μB/atom

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Co5N-1

-7.18628

I 4/m

M(Co) = 1.34783 μB/atom

MAE = -2.13 MJ/m3

Co5N-2

-7.18555

C 2/m 2/c 21/m

M(Co = 1.49111 μB/atom

MAE = 0.72 MJ/m3

Co5N-3

-7.18548

C 2/m 2/m 2/m

M(Co) = 1.51193 μB/atom

Co5N-4

-7.17957

C 1 2 1

M(Co) = 1.27999 μB/atom

MAE = -0.32 MJ/m3

Co5N-5

-7.17695

C 1 2/c 1

M(Co) = 1.4217 μB/atom

Co5N-6

-7.16747

C 2/m 2/c 21/m

M(Co) = 1.40351 μB/atom

Co5N-7

-7.16641

C 2 2 21

M(Co) = 1.28129 μB/atom

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Co6N-1

-7.15608

C 1 2/m 1

M(Co) = 1.34556 μB/atom

MAE = -0.64 MJ/m3

Co6N-2

-7.15429

P 4/m 2/m 2/m

M(Co) = 1.57263 μB/atom

MAE = 0.54 MJ/m3

Co6N-3

-7.15169

P -1

M(Co) = 1.48053 μB/atom

Co6N-4

-7.15089

C 2/m 2/m 2/a

M(Co) = 1.38944 μB/atom

Co6N-5

-7.14364

I 21/m 21/m 21/a

M(Co) = 1.42151 μB/atom

Co6N-6

-7.13778

R -3 (hexagonal axes)

M(Co) = 1.38047 μB/atom

Co6N-7

-7.13566

P 21/n 21/n 2/m

M(Co) = 1.4084 μB/atom

MAE = 0.79 MJ/m3

Co6N-8

-7.13479

P -3 1 2/m

M(Co) = 1.43817 μB/atom

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Co7N-1

-7.14381

P -1

M(Co) = 1.35954 μB/atom

Co7N-2

-7.13785

C 1 2/c 1

M(Co) = 1.35976 μB/atom

Co7N-3

-7.13699

C 2/m 2/m 2/m

M(Co) = 1.56855 μB/atom

MAE = -0.66 MJ/m3

Co7N-4

-7.13674

C 2/m 2/c 21/m

M(Co) = 1.54464 μB/atom

Co7N-5

-7.12404

C 2/m 2/c 21/m

M(Co) = 1.44689 μB/atom

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Co8N-1

-7.13772

F 4/m -3 2/m

M(Co) = 1.43014 μB/atom

Co8N-2

-7.13517

C 1 2/m 1

M(Co) = 1.50829 μB/atom

MAE = -0.89 MJ/m3

Co8N-3

-7.13488

C 1 2/m 1

M(Co) = 1.45073 μB/atom

Co8N-4

-7.13439

C 2/m 2/m 2/m

M(Co) = 1.35626 μB/atom

Co8N-5

-7.1331

P 21 21 2

M(Co) = 1.376 μB/atom