Crystal structure, T-P phase diagram and Crystal structure, T-P phase diagram and magnetotransport properties of new organic metal magnetotransport properties of new organic metal

-(BETS)-(BETS)22Mn[N(CN)Mn[N(CN)22]]33

Vladimir Zverev1, Nataliya Kushch2, Eduard Yagubskii2, Lev Buravov2, Salavat Khasanov1, Rimma Shibaeva1, Mark Kartsovnik3, and Werner Biberacher3

1 Institute of Solid State Physics, Chernogolovka2 Institute of Problems of Chemical Physics, Chernogolovka3 Walther-Meissner-Institut, Bayerishe Akademie der Wissenschaften, Garching, Germany

Crystal structure, T-P phase diagram and Crystal structure, T-P phase diagram and magnetotransport properties of new organic metal magnetotransport properties of new organic metal

-(BETS)-(BETS)22Mn[N(CN)Mn[N(CN)22]]33

Electrical conductivity is provided by an organic radical cation subsystem

We deal with hybrid multifunctional molecular material combining conducting and magnetic properties in the same crystal lattice.

Magnetism is provided by an anionic subsystem, containing magnetic transition metal (Mn).

a b

Crystal structure of -(BETS)2Mn[N(CN)2]3 projected on the ac-plane (a); Projection of the anion layer on the bc-plane (b)

The structure is characterized by the alternation of -type cation layers with polymeric anion layers along the a axis. In the anion layer, each Mn2+ ion has an octahedral coordination and is linked with six neighboring Mn2+ ions via N(CN)2 - bridges.

Y

Y

+q -q

(0 1 -3)

(0 -1 -3)

q = 0.42 b*

-(BETS)2Mn[N(CN)2]3

T = 90K

Diffraction pattern in the (a*,b*) plane.The arrows indicate on the satellite reflections.

1-D section of the diffraction pattern along the line Y = kb* - 3c*

There is a phase transition near 102 K resulting in the formation of incommensurate superstructure: below 102K X-ray diffraction patterns show weak satellite reflections which can be described by the incommensurate wave vector q = 0.42b*. This superstructure survives down to 15 K!

Y

-(BETS)2Mn[N(CN)2]3

T = 90K

Diffraction pattern in the (a*,b*) plane.The arrows indicate on the satellite reflections.

There is a phase transition near 102 K resulting in the formation of incommensurate superstructure: below 102K X-ray diffraction patterns show weak satellite reflections which can be described by the incommensurate wave vector q = 0.42b*. This superstructure survives down to 15 K!

60 80 100 120

4500

5000

5500

R (

Oh

m)

T (K)

Temperature dependence of the interplane resistance of -(BETS)2Mn[N(CN)2]3 crystal at ambient pressure

0 50 100 150 200 250 3004

5

6

7

8

9

10

11

R (

k)

T (K)

TM-I

Temperature dependence of the interplane resistance of -(BETS)2Mn[N(CN)2]3 crystal at ambient pressure

0 50 100 150 200 250 3004

5

6

7

8

9

10

11

R (

k)

T (K)

TM-I

The M-I transition takes place in electron subsystem because at T=TM-I there are no changes in the X-ray crystal structure!

0 100 200 3000

1

2

3

4

5

0 10 20 300

5

x

106 , m

3 /mol

T, K

0H = 7T;

H // b

0H = 0.1T

T, K

1/ x

10-7,

mol

/m3

Susceptibility in -(BETS)2[Mn(N(CN)2)3]

0 100 200 3000

1

2

3

4

5

0 10 20 300

5

x 1

06 , m3 /m

ol

T, K

0H = 7T;

H // b

0H = 0.1T

T, K

1/ x

10-7,

mol

/m3

Susceptibility in -(BETS)2[Mn(N(CN)2)3]

There is no peculiarity on (T) dependence at TM-I

0 100 200 3000

1

2

3

4

5

0 10 20 300

5

x 1

06 , m3 /m

ol

T, K

0H = 7T;

H // b

0H = 0.1T

T, K

1/ x

10-7,

mol

/m3

Susceptibility in -(BETS)2[Mn(N(CN)2)3]

There is no peculiarity on (T) dependence at TM-I

But in 1H NMR and torque experiments

there are some peculiarities indicating to the formation of a short-range order of Mn spins at TM-I !

See Oleg Vyaselev’s Poster!

Pressure induced metal-insulator andsuperconductor-insulator transitions in

-(BETS)2Mn[N(CN)2]3

0 5 10 15 20 25 30 35101

102

103

104

105

R

()

T (K)

P=0 kbar0.20.4

0.61.0

1.41.8

T – P phase diagram

0.1 10

10

20

30

T (

K)

P (kbar)

Insulator

Metal

Superconductor

Tc

TM-I

Superconducting and insulating phases coexist at (0.4 < P < 0.5) kbar.

Shubnikov – de Haas oscillations

0 2 4 6 8 10 12 14 160

200

400

600

800

1000

1200

1400

1600

R

()

B (T)

P=1 kbar, T=1.4 K, B||a

Shubnikov – de Haas oscillations

0 2 4 6 8 10 12 14 160

200

400

600

800

1000

1200

1400

1600

8 10 12 14-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

R ()

B (T)

R

()

B (T)

P=1 kbar, T=1.4 K, B||a

SdH oscillations in 1/B scale

0.06 0.08 0.10 0.12

-0.5

0.0

0.5

0

1

2

3

4

5

6

R ()

1/B (T-1)

n

P=1.0 kbarF=87.5 T

Temperature dependence of SdH oscillation amplitude

8 9 10 11 12 13 14 15 16-2

-1

0

1

R (

)

B (T)

1.4K

1.75K

2.22K

2.6K

3.21KP=1.8 kbar

1.5 2.0 2.5 3.0

-5.0

-4.5

-4.0

-3.5

-3.0

-2.5

ln(A

/T)

T (K)

P=1.8 kbarmc/m0=0.89

Pressure dependences of SdH oscillation frequency and the cyclotron mass

0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.675

80

85

90

95

100

0.75

0.80

0.85

0.90

0.95

1.00

1.05

1.10

F (

T)

P (kbar)

mc/

m0

Energy spectrum and the Fermi-surface (extended Hückel method)

The SdH oscillation frequency corresponds to about 1.5% of the BZ cross section.

Y

Y

+q -q

(0 1 -3)

(0 -1 -3)

q = 0.42 b*

-(BETS)2Mn[N(CN)2]3

T = 90K

Diffraction pattern in the (a*,b*) plane.The arrows indicate on the satellite reflections.

1-D section of the diffraction pattern along the line Y = kb* - 3c*

There is a phase transition near 102 K resulting in the formation of incommensurate superstructure: below 102K X-ray diffraction patterns show weak satellite reflections which can be described by the incommensurate wave vector q = 0.42b*. This superstructure survives down to 15 K!

Energy spectrum and the Fermi-surface (extended Hückel method)

The SdH oscillation frequency corresponds to about 1.5% of the BZ cross section.

The small pocket may arise due to the existence of the superstructure! q=0.42b*

Conclusions

• Crystal structure and magnetotransport properties of new organic metal -(BETS)2Mn[N(CN)2]3 were studied. • A phase transition near 102 K resulting in the formation of incommensurate superstructure below 102K was found. • At T 27K a structureless phase transition in electron system was observed at ambient pressure. • A moderate pressure P 0.5 kbar suppresses the metal-insulator transition and the compound becomes metallic down to low temperatures and superconducting with Tc= 5.8 K. • T-P phase diagram was plotted in the pressure range 0-2.5 kbar.• In the metallic state Shubnikov-de Haas oscillations which could be related to the small pockets of the FS were observed .

Temperature dependence of the interplane resistance of -(BETS)2Mn[N(CN)2]3 crystal at ambient pressure

0 50 100 150 200 250 3004

5

6

7

8

9

10

11

R (

k)

T (K)