Combined study of Schwinger-boson mean-field theory and linearized tensor renormalization group on Heisenberg ferromagnetic mixed spin (S, σ) chains
The Schwinger-boson mean-field theory (SBMFT) and the linearized tensor renormalization group (LTRG) methods are complementarily applied to explore the thermodynamics of the quantum ferromagnetic mixed spin (S, σ) chains. It is found that the system has double excitations, i.e. a gapless and a gappe...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
AIP Publishing LLC
2015-07-01
|
| Series: | AIP Advances |
| Online Access: | http://dx.doi.org/10.1063/1.4927854 |
| _version_ | 1818940105331572736 |
|---|---|
| author | Xin Yan Zhen-Gang Zhu Gang Su |
| author_facet | Xin Yan Zhen-Gang Zhu Gang Su |
| author_sort | Xin Yan |
| collection | DOAJ |
| description | The Schwinger-boson mean-field theory (SBMFT) and the linearized tensor renormalization group (LTRG) methods are complementarily applied to explore the thermodynamics of the quantum ferromagnetic mixed spin (S, σ) chains. It is found that the system has double excitations, i.e. a gapless and a gapped excitation; the low-lying spectrum can be approximated by
ω
k
∼
S
σ
2
(
S
+
σ
)
J
k
2
with J the ferromagnetic coupling; and the gap between the two branches is estimated to be △ ∼ J. The Bose-Einstein condensation indicates a ferromagnetic ground state with magnetization
m
tot
z
=
N
(
S
+
σ
)
. At low temperature, the spin correlation length is inversely proportional to temperature (T), the susceptibility behaviors as
χ
=
a
1
∗
1
T
2
+
a
2
∗
1
T
, and the specific heat has the form of
C
=
c
1
∗
T
−
c
2
∗
T
+
c
3
∗
T
3
2
, with ai (i = 1, 2) and ci (i = 1, 2, 3) the temperature independent constants. The SBMFT results are shown to be in qualitatively agreement with those by the LTRG numerical calculations for S = 1 and σ = 1/2. A comparison of the LTRG results with the experimental data of the model material MnIINiII(NO2)4(en)2(en = ethylenediamine), is made, in which the coupling parameters of the compound are obtained. This study provides useful information for deeply understanding the physical properties of quantum ferromagnetic mixed spin chain materials. |
| first_indexed | 2024-12-20T06:34:21Z |
| format | Article |
| id | doaj.art-4e82e5ca257841f49e0c40a4d228f991 |
| institution | Directory Open Access Journal |
| issn | 2158-3226 |
| language | English |
| last_indexed | 2024-12-20T06:34:21Z |
| publishDate | 2015-07-01 |
| publisher | AIP Publishing LLC |
| record_format | Article |
| series | AIP Advances |
| spelling | doaj.art-4e82e5ca257841f49e0c40a4d228f9912022-12-21T19:50:02ZengAIP Publishing LLCAIP Advances2158-32262015-07-0157077183077183-1710.1063/1.4927854084507ADVCombined study of Schwinger-boson mean-field theory and linearized tensor renormalization group on Heisenberg ferromagnetic mixed spin (S, σ) chainsXin Yan0Zhen-Gang Zhu1Gang Su2Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory, College of Physical Sciences, University of Chinese Academy of Sciences, P. O. Box 4588, Beijing 100049, ChinaTheoretical Condensed Matter Physics and Computational Materials Physics Laboratory, College of Physical Sciences, University of Chinese Academy of Sciences, P. O. Box 4588, Beijing 100049, ChinaTheoretical Condensed Matter Physics and Computational Materials Physics Laboratory, College of Physical Sciences, University of Chinese Academy of Sciences, P. O. Box 4588, Beijing 100049, ChinaThe Schwinger-boson mean-field theory (SBMFT) and the linearized tensor renormalization group (LTRG) methods are complementarily applied to explore the thermodynamics of the quantum ferromagnetic mixed spin (S, σ) chains. It is found that the system has double excitations, i.e. a gapless and a gapped excitation; the low-lying spectrum can be approximated by ω k ∼ S σ 2 ( S + σ ) J k 2 with J the ferromagnetic coupling; and the gap between the two branches is estimated to be △ ∼ J. The Bose-Einstein condensation indicates a ferromagnetic ground state with magnetization m tot z = N ( S + σ ) . At low temperature, the spin correlation length is inversely proportional to temperature (T), the susceptibility behaviors as χ = a 1 ∗ 1 T 2 + a 2 ∗ 1 T , and the specific heat has the form of C = c 1 ∗ T − c 2 ∗ T + c 3 ∗ T 3 2 , with ai (i = 1, 2) and ci (i = 1, 2, 3) the temperature independent constants. The SBMFT results are shown to be in qualitatively agreement with those by the LTRG numerical calculations for S = 1 and σ = 1/2. A comparison of the LTRG results with the experimental data of the model material MnIINiII(NO2)4(en)2(en = ethylenediamine), is made, in which the coupling parameters of the compound are obtained. This study provides useful information for deeply understanding the physical properties of quantum ferromagnetic mixed spin chain materials.http://dx.doi.org/10.1063/1.4927854 |
| spellingShingle | Xin Yan Zhen-Gang Zhu Gang Su Combined study of Schwinger-boson mean-field theory and linearized tensor renormalization group on Heisenberg ferromagnetic mixed spin (S, σ) chains AIP Advances |
| title | Combined study of Schwinger-boson mean-field theory and linearized tensor renormalization group on Heisenberg ferromagnetic mixed spin (S, σ) chains |
| title_full | Combined study of Schwinger-boson mean-field theory and linearized tensor renormalization group on Heisenberg ferromagnetic mixed spin (S, σ) chains |
| title_fullStr | Combined study of Schwinger-boson mean-field theory and linearized tensor renormalization group on Heisenberg ferromagnetic mixed spin (S, σ) chains |
| title_full_unstemmed | Combined study of Schwinger-boson mean-field theory and linearized tensor renormalization group on Heisenberg ferromagnetic mixed spin (S, σ) chains |
| title_short | Combined study of Schwinger-boson mean-field theory and linearized tensor renormalization group on Heisenberg ferromagnetic mixed spin (S, σ) chains |
| title_sort | combined study of schwinger boson mean field theory and linearized tensor renormalization group on heisenberg ferromagnetic mixed spin s σ chains |
| url | http://dx.doi.org/10.1063/1.4927854 |
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